[noun - seismology & plate tectonics] A “ripple” wave produced by an earthquake. The “S” is from the Italian “Segundo,” indicating that S-waves arrived at seismic stations after the P-waves.

• Appears in modules:

• Earth Structure

[person] American astronomer and astrochemist, born in Brooklyn, New York (1934-1996). Sagan was a pioneer in astrobiology, and championed the Search for Extra-Terrestrial Intelligence (SETI). He was also a prolific researcher: He was key in the determination of Venus's high surface temperature, was an early proponent of oceans on Titan and Europa, and studied planetary atmospheres. He is best remembered for hosting the TV series Cosmos and for writing a widely popular companion book by the same name.

• Appears in modules:

• Origins of Life I
• Peer Review in Scientific Publishing

[person] (December 16, 1805 – November 10, 1861) French zoologist. He created the term 'ethology', which is the branch of zoology consisting of studying animals in their natural habitats. In 1832-1837 Saint-Hilaire published his most famous work, Histoire générale et particulière des anomalies de l'organisation chez l'homme et les animaux (General and Particular History of Structural Monstrosities in Man and Animals). In it, he introduced the term teratology for the study of congenital abnormalities in animals.

[noun - compounds, physical & chemical properties] Generally, any ionic compound except those that contain hydroxide or hydrogen ions. Specifically, any compound other than water formed by the reaction of an acid and a base. In common usage, the term salt, or table salt, refers to the ionic compound sodium chloride, NaCl.

• Appears in modules:

• Atomic Theory II
• Chemical Bonding
• Chemical Equations
• Chemical Reactions
• Defining Minerals
• Diffusion I
• Factors that Control Earth's Temperature
• Gene Expression
• Introduction to Inferential Statistics
• Meselson and Stahl
• Properties of Liquids
• Properties of Solids

[noun - research methods] The process of collecting data to be studied; the gathering of a representative part of a larger group in order to determine characteristics of the entire population.

• Appears in modules:

• Confidence Intervals
• Description in Scientific Research
• Future of Human Evolution
• History of Earth's Atmosphere I
• Introduction to Descriptive Statistics
• Introduction to Inferential Statistics
• Kevin Arrigo
• Statistics in Science

[noun] Hygiene measures such as waste disposal that promote cleanliness and prevent the spread of disease.

• Appears in modules:

• Carlos J. Finlay

[noun - biomolecules, physical & chemical properties] The process of converting a fat or an oil into soap through combination with an alkali.

• Appears in modules:

• Lipids

[noun] An instrument for measuring heat energy or weight in which units are marked at intervals; a system for quantifying heat energy based on reference points such as the freezing point and boiling point. The three most common temperature scales are the Celsius, Fahrenheit, and Kelvin scales.

• Appears in modules:

• Acids and Bases I
• Acids and Bases II
• Confidence Intervals
• Diffusion I
• Energy
• Properties of Minerals
• Stoichiometry
• Temperature
• The Mole and Atomic Mass
• The Rock Cycle
• Thermodynamics I

[person - cells] German botanist born in Hamburg (1804-1881). Schleiden determined the importance of the nucleus in cellular propagation and, with Theodor Schwann, is credited with establishing the foundations of the cell theory.

• Appears in modules:

• Discovery and Structure of Cells

[noun - atoms & subatomic particles, atoms & subatomic particles, modern physics] A partial differential equation developed by Erwin Schrodinger that describes the change of the quantum state of a physical system over time. The equation correctly predicts the parameters of the energy levels of atomic orbitals, and can be used to generate probability maps for the s, p, d and f orbitals:
iℏ (∂/∂t) Ψ = HΨ
where i is the imaginary unit, ℏ is Planck’s constant over 2Π, t is time, H is the Hamiltonian operator, and Ψ is the wave-function.

• Appears in modules:

• Atomic Theory III
• Atomic Theory IV

[person - atoms & subatomic particles, energy, atoms & subatomic particles, energy, modern physics] Austrian physicist instrumental in the development of quantum theory and for his known for the Schrödinger equation. 1933 Nobel Prize winner for "the discovery of new productive forms of atomic theory."

• Appears in modules:

• Atomic Theory III

[person - cells] German physiologist and histologist born in Neuss, Germany (1810-1882). Schwann cofounded (with Matthias Schleiden) the cell theory. He elaborated on Schleiden's work and showed that cells are the basis of both plant and animal tissue. He also demonstrated that yeast is an organism and published Microscopical Researches in the Structure and Growth of Animals and Plants (1839, translation 1847).

• Appears in modules:

• Santiago Ramón y Cajal and Camillo Golgi

[noun] A sustained debate within the broader scientific community, in which arguments are supported by data. See our module Scientific Controversy.

• Appears in modules:

• Scientific Controversy
• Understanding Scientific Journals and Articles

[noun - scientific tools & techniques, scientific concepts] A scientific process of investigation and discovery involving a variety of techniques such as systematic observation, description, measurement, experimentation, modeling and the formulation, testing, and modification of hypotheses.

• Appears in modules:

• The Practice of Science

[noun - equations] A method of expressing numbers in terms of a decimal number greater than or equal to 1 and less than 10 multiplied by a power of 10.

• Appears in modules:

• Linear Equations in Science
• Scientific Notation and Order of Magnitude
• The Metric System

[noun] A term first coined by Alexandre Koyré in 1939, it refers to the remarkable scientific advances roughly extending from the publication of De Revolutionibus Orbium Coelestium by Nicolaus Copernicus in 1543 to the death of Isaac Newton in 1727. For more information, see our module The Practice of Science.

• Appears in modules:

• Scientific Institutions and Societies
• The Practice of Science
• The Rock Cycle

[noun - oceanography] frozen seawater that floats on the ocean surface

[noun - oceanography, seismology & plate tectonics] The bottom surface of the ocean.

• Appears in modules:

• History of Earth's Atmosphere II
• Luis Walter Alvarez
• Origins of Plate Tectonic Theory
• Plates, Plate Boundaries, and Driving Forces
• The Carbon Cycle
• Theories, Hypotheses, and Laws

[noun - landforms & geologic formations, oceanography, rock cycle, seismology & plate tectonics] The mechanism proposed by Harry Hess which drives plate tectonics. According to this theory, new magma is formed at divergent boundaries, pushing plates away from each other as if on a conveyor belt.

• Appears in modules:

• Origins of Plate Tectonic Theory

[noun - landforms & geologic formations, oceanography, seismology & plate tectonics] An extinct volcano which has been eroded by ocean waves, resulting in a flat-topped feature just beneath the surface of the ocean. 

• Appears in modules:

• Plates, Plate Boundaries, and Driving Forces

[noun - atoms & subatomic particles, energy] The energy required to remove one mole of electrons, from one mole of singly charged (positive) gaseous ions, to form one mole of doubly charged (positive) gaseous ions.

• Appears in modules:

• Atomic Theory II

[noun - laws & theories, energy, scientific concepts, thermodynamics] One of three Laws of Thermodynamics, or laws relating to heat power. The Second Law is commonly referred to as the Law of Increased Entropy. During the conversion of energy from one form to another, some energy is lost to the process of conversion. Though the total energy is in fact conserved (see the First Law of Thermodynamics), a portion becomes unusable as it increases disorder and randomness within the system.

• Appears in modules:

• The Nature of Scientific Knowledge
• Thermodynamics I

[noun - compounds, rock cycle] Loose, unconsolidated material of the following compositions:
1. rock fragments (also called clasts) transported by wind, moving water, or moving ice, such as sand
2. chemical precipitates from solution, such as salt
3. organic secretions or accumulation, such as coal

• Appears in modules:

• Comparison in Scientific Research
• Defining Minerals
• History of Earth's Atmosphere II
• Linear Equations in Science
• Modeling in Scientific Research
• The Carbon Cycle
• The Hydrologic Cycle
• The Nitrogen Cycle
• The Phosphorus Cycle
• The Rock Cycle
• Theories, Hypotheses, and Laws
• Utilizing the Scientific Literature

[adjective - landforms & geologic formations, rock cycle, rocks & minerals] Formed from the deposition or precipitation of sediments. Sedimentary rocks consist of sediments that have been compacted and cemented together.

• Appears in modules:

• Description in Scientific Research
• Factors that Control Regional Climate
• History of Earth's Atmosphere II
• Modeling in Scientific Research
• The Phosphorus Cycle
• The Rock Cycle
• The Silicate Minerals
• Utilizing the Scientific Literature

[noun - seismology & plate tectonics] A form of sound wave that travels away from the source of an earthquake. There are several types of seismic waves, but S-waves and P-waves are the most commonly measured and recognized.

• Appears in modules:

• Earth Structure

[noun - seismology & plate tectonics] A scientist who studies earthquakes and the behavior of seismic waves in the Earth.

• Appears in modules:

• Earth Structure
• Statistics in Science

[noun - medicine] The identification and study of bodily fluids, specifically the serum in blood. Often, researchers use the term serology to refer to diagnostic testing to identify antibodies, antigens, and other substances in the serum.

• Appears in modules:

• Blood Biology I

[noun - rocks & minerals] A mineral formed from hydrothermal metamorphism of basalt. The rock “serpentinite” is composed entirely of serpentine, and is very common in Northern California, and it weathers to create a nutrient-poor, heavy metal-rich soil.

• Appears in modules:

• The Nitrogen Cycle

[noun - anatomy & physiology, medicine] (Plural: sera) The liquid portion of whole blood after other material (cells and clotting factors) are removed. Blood serum does contain the antibodies and antigens, though, and is often used for diagnostic tests.

• Appears in modules:

• Blood Biology I
• César Milstein
• Chemical Reactions

[noun - landforms & geologic formations] Although it is commonly called a "volcanic neck," Shiprock (located near the Four Corners of Utah, Colorado, Arizona, and New Mexico) is a remnant of a single explosive volcanic eruption rather than a long-lived volcano. The magma involved in the eruption started more than 100 km below the Earth's surface, in the mantle.

• Appears in modules:

• Earth Structure

[acronym - units of measurement] Système international d'unités (French for "International System of Units," abbreviated to SI) is a system of standard units introduced to remove barriers to international trade, based on the older metric system.

• Appears in modules:

• Atomic Theory I
• Atomic Theory II
• Barbara McClintock
• Biodiversity I
• Bone Changes in Rock Climbers
• Carlos J. Finlay
• Cell Division I
• Cell Division II
• Cellular Organelles I
• César Milstein
• Charles Darwin I
• Charles Darwin II
• Charles Darwin III
• Chemical Bonding
• Chemical Reactions
• Composition of Earth's Atmosphere
• Confidence Intervals
• Creativity in Science
• Defining Minerals
• Density
• Diffusion I
• Discovery and Structure of Cells
• DNA I
• DNA II
• DNA III
• Early Ideas about Matter
• Earth Structure
• Ellen Ochoa
• Energy
• Exponential Equations in Science I
• Exponential Equations in Science II
• Fabiola León-Velarde
• Factors that Control Earth's Temperature
• Factors that Control Regional Climate
• Fats and Proteins
• France Anne-Dominic Córdova
• Franklin Chang Díaz
• Gravity
• History of Earth's Atmosphere II
• Introduction to Descriptive Statistics
• Introduction to Inferential Statistics
• Kevin Arrigo
• Kinetic-Molecular Theory
• Light I
• Linear Equations in Science
• Mario Molina
• Measurement
• Membranes I
• Membranes II
• Mendel and Independent Assortment
• Mendel and Inheritance
• Meselson and Stahl
• Nuclear Chemistry
• Photosynthesis I
• Properties of Gases
• Properties of Minerals
• Properties of Solids
• Scientific Notation and Order of Magnitude
• Sergio Avila
• States of Matter
• Taxonomy I
• Taxonomy II
• Temperature
• The Carbon Cycle
• The Case of the Ivory-billed Woodpecker
• The Hydrologic Cycle
• The Metric System
• The Mole and Atomic Mass
• The Nature of Scientific Knowledge
• The Periodic Table of Elements
• The Phosphorus Cycle
• The Process of Science
• The Rock Cycle
• The Scientific Method
• Thermodynamics I
• Unit Conversion
• Wave Mathematics
• Waves and Wave Motion

[noun - genetics & inheritance, medicine] An inherited blood disorder characterized by irregularly shaped red blood cells. These sickle-shaped cells get wedged in small blood vessels, disrupting the flow of blood and oxygen through the body.

• Appears in modules:

• Future of Human Evolution
• Population Genetics

[noun - statistics] In statistics, a skewed distribution is one that exhibits asymmetry in the probability distribution of a random variable. Large differences in the mean compared to the median of a dataset can indicate a skewed distribution of data values. Compare the graph at left below to the normal distribution graph at right.

[person - biomolecules, cells, organic & biochemistry] Danish medical doctor born in Lemvig, Denmark (1918-). Skou's early work in local anesthetics led him to investigate the sodium-potassium pump. In 1997, Skou was awarded a Nobel Prize for his work on cation transport across cell membranes.

• Appears in modules:

• Absorption, Distribution, and Storage of Chemicals

[noun - biodiversity & ecological relationships, bioregions, biomes & ecosystems] A forested mountaintop or highland surrounded and isolated by large lowland areas of a different biome, such as desert or grassland. Sky islands are often rich a habitat for wildlife and home to rare or endemic species.

• Appears in modules:

• Sergio Avila

[person - planetary science, cosmology] Astronomer, born in Indiana, United States (1875-1969). Slipher was responsible for the discoveries of both galactic redshifts and the sodium layer, as well as involved in the work that led to the discovery of Pluto. Slipher's measurement of redshifts in spiral nebulae provided early evidence in support of the Big Bang Theory.

[noun - atmospheric science] A photochemical haze caused by the action of solar ultraviolet radiation on atmosphere polluted with hydrocarbons and oxides of nitrogen.

• Appears in modules:

• The Nitrogen Cycle

[noun - science communication] A group of people who belong to an organization that has been formed because of shared interest in a specific field.

• Appears in modules:

• Description in Scientific Research
• Factors that Control Regional Climate
• France Anne-Dominic Córdova
• Light I
• Mario Molina
• Origins of Life I
• Ruth Benerito
• Scientific Ethics
• Scientific Institutions and Societies
• Scientists and the Scientific Community
• Statistics in Science
• The How and Why of Scientific Meetings
• The Process of Science
• Theories, Hypotheses, and Laws
• Thermodynamics I
• Understanding Scientific Journals and Articles
• Utilizing the Scientific Literature

[person] British physicist born in Eastbourne, Sussex (1877-1956). He studied radioactivity with Ernest Rutherford, jointly concluding that radioactivity consisted of atomic disintegration (of parent atoms) and the formation of new kinds of matter (daughter products). Soddy articulated the Displacement Law, which states that an element which emits an alpha particle moves two places back on the Periodic Table. He also came up with the concept of isotopes. In 1921, he was awarded the Nobel Prize in Chemistry.

• Appears in modules:

• Nuclear Chemistry

[noun - landforms & geologic formations] The loose top layer of Earth’s surface where plants grow, made up of particles of rocks, minerals, and organic material.

• Appears in modules:

• Biodiversity I
• César Milstein
• Defining Minerals
• Diffusion I
• History of Earth's Atmosphere II
• Peer Review in Scientific Publishing
• Photosynthesis I
• Scientific Controversy
• Sergio Avila
• Stoichiometry
• The Carbon Cycle
• The Hydrologic Cycle
• The Nitrogen Cycle
• The Phosphorus Cycle
• The Piltdown Hoax
• The Silicate Minerals

[noun - solar and lunar processes] A celestial event occurring when the Moon passes between the Sun and the Earth such that the Sun is wholly or partially obscured. At least two and up to five solar eclipses occur each year on Earth, with between zero and two of them being total eclipses.

• Appears in modules:

• Description in Scientific Research

[noun - materials science, matter, physical & chemical properties] A collection of atoms or molecules that are held together so that, under constant conditions, they maintain a defined shape and size. The two main categories of solids are crystalline and amorphous.

• Appears in modules:

• Acids and Bases II
• Blood Biology I
• Chemical Bonding
• Chemical Equations
• Defining Minerals
• Density
• Diffusion I
• Early Ideas about Matter
• Earth Structure
• Energy
• History of Earth's Atmosphere II
• Kinetic-Molecular Theory
• Lipids
• Properties of Liquids
• Properties of Minerals
• Properties of Solids
• Solutions, Solubility, and Colligative Properties
• States of Matter
• The Carbon Cycle
• The Mole and Atomic Mass
• The Nature of Scientific Knowledge
• The Periodic Table of Elements
• The Silicate Minerals
• Water

[noun - matter, physical & chemical properties] The extent to which a solid dissolves in a particular solvent.

• Appears in modules:

• Acids and Bases I
• Properties of Liquids
• Properties of Solids
• Solutions, Solubility, and Colligative Properties

[adjective - compounds] Capable of being dissolved.

• Appears in modules:

• Absorption, Distribution, and Storage of Chemicals
• Chemical Reactions
• Creativity in Science
• DNA II
• DNA III
• History of Earth's Atmosphere II
• Lipids
• Membranes I
• Origins of Life II
• Properties of Liquids
• Properties of Solids
• Solutions, Solubility, and Colligative Properties
• Water

[noun - compounds, matter, physical & chemical properties] A compound dissolved in a solvent to create a solution.

• Appears in modules:

• Lipids
• Properties of Liquids
• Solutions, Solubility, and Colligative Properties

[noun] A mixture of more than one substance with properties that do not vary within the sample. Commonly used to describe a solid dissolved in a liquid, solutions of two or more gases, liquids, solid metals, or other materials also exist. Also called a homogeneous mixture.

• Appears in modules:

• Atomic Theory IV
• Chemical Equations
• Creativity in Science
• Diffusion I
• DNA III
• Energy Metabolism I
• Membranes II
• Meselson and Stahl
• Photosynthesis I
• Properties of Liquids
• Properties of Solids
• Ruth Benerito
• Santiago Ramón y Cajal and Camillo Golgi

[noun] The most abundant component in a homogeneous mixture of two or more substances.

• Appears in modules:

• Chemical Bonding
• Membranes I
• Properties of Liquids
• Properties of Solids

[noun - oceanography] A technique to transmit high-frequency sound waves through water then measure how long it takes for the waves to be reflected and returned. Used as a means for detecting the depth of water or for finding objects under water.

• Appears in modules:

• Data Analysis and Interpretation
• Diffusion I
• Measurement
• Origins of Plate Tectonic Theory
• Statistics in Science
• Thermodynamics I
• Uncertainty, Error, and Confidence

[noun - space exploration] A journey to space by a spacecraft for a particular purpose, such as to collect scientific data.

• Appears in modules:

• Franklin Chang Díaz

[noun - space exploration] A spacecraft that carries people and cargo between Earth and outer space.

• Appears in modules:

• Ellen Ochoa
• Franklin Chang Díaz
• Modeling in Scientific Research

[person - organisms] Italian microscopist and biologist, born in Scandiano (1729-1799). He investigated spontaneous generation of microorganisms in broth and herbal infusions. Spallanzani also studied the circulatory system, pioneered artificial insemination, and proposed that bats navigate by echolocation.

• Appears in modules:

• Experimentation in Scientific Research
• Origins of Life I

[noun] The inquisition, initiated in 1478 by King Ferdinand and Queen Isabella, which protected the orthodoxy of Catholicism in Spain.

[noun - evolution & adaptation, organisms] 1. In biological classifications, it is the lowest and most basic unit of the Linnaean taxonomic hierarchy (although it is also divisible into subspecies), and one of the two required titles of a binomial name. In nature, a species is a group of organisms that breed only amongst themselves and produce offspring that are also capable of reproducing. 2. In chemistry, a group of constituents or molecules, that share major chemical similarities. For example, Hg⁰ and Hg⁺², or CO and CO₂.

• Appears in modules:

• Adaptation
• Animal Behavior
• Atomic Theory II
• Atomic Theory IV
• Biodiversity I
• Carlos J. Finlay
• Cell Division I
• Cell Division II
• Cellular Organelles I
• Charles Darwin I
• Charles Darwin II
• Charles Darwin III
• Chemical Bonding
• Chemical Reactions
• DNA II
• DNA III
• Fabiola León-Velarde
• Introduction to Descriptive Statistics
• Kevin Arrigo
• Linear Equations in Science
• Mendel and Independent Assortment
• Mendel and Inheritance
• Origins of Plate Tectonic Theory
• Santiago Ramón y Cajal and Camillo Golgi
• Scientific Ethics
• Scientists and the Scientific Community
• Sergio Avila
• Taxonomy I
• Taxonomy II
• The Carbon Cycle
• The Nitrogen Cycle
• The Piltdown Hoax
• Theories, Hypotheses, and Laws
• Using Graphs and Visual Data in Science
• Utilizing the Scientific Literature
• Y-Chromsome and Mitochondrial DNA Haplotypes

[noun - atoms & subatomic particles] See line spectra.

• Appears in modules:

• Atomic Theory II
• Atomic Theory III

[noun] A visual image of how the spectrum of a wave signal changes over time. Spectrograms have applications in seismology, ornithology, phonetics, and many other disciplines dealing with waves.

• Appears in modules:

• The Nature of Scientific Knowledge

[noun - electromagnetism, light & optics] An instrument that separates the waves emitted from an object into its corresponding spectrum of wavelengths. These wavelengths can be mapped to identify properties of the light source (e.g., intensity, movement, elemental composition, etc.). Spectrographs vary depending on the wave type being analyzed. See spectrogram and spectrometer.

• Appears in modules:

• The Nature of Scientific Knowledge

[noun - research tools] An instrument that measures the intensity of radiation, including light, as a function of its wavelength. Because different substances, including elements and compounds, both absorb and emit specific wavelengths of radiation, spectrometers can be used to measure the composition of distant stars and planets, as well as the composition of various samples on earth including soil, water, minerals, and gases.

• Appears in modules:

• Description in Scientific Research
• History of Earth's Atmosphere I
• Properties of Minerals

[noun - research methods] The study of the interaction of radiation (electromagnetic or particle radiation) and matter. An analytical technology used for the identification of substances based on the spectrum of radiation absorbed or emitted by different substances.

• Appears in modules:

• Scientists and the Scientific Community

[noun - electromagnetism, light & optics] (plural: spectra) A continuing range such as of color or frequency; a series of colors arranged by wavelength as in a rainbow.

• Appears in modules:

• Acids and Bases II
• Atomic Theory II
• Atomic Theory IV
• Experimentation in Scientific Research
• Factors that Control Earth's Temperature
• History of Earth's Atmosphere I
• Light and Electromagnetism
• Photosynthesis I
• Properties of Liquids
• Scientific Controversy
• The Nature of Scientific Knowledge
• Theories, Hypotheses, and Laws

[noun] Shaped like a sphere.

• Appears in modules:

• Atomic Theory IV
• Origins of Life II
• Properties of Liquids
• The Nature of Scientific Knowledge

[noun - stellar and galactic astronomy] (or spiral galaxy) A galaxy that has a spiral structure, such as the Milky Way. The older stars are concentrated toward the center of spiral nebulae, while younger stars occupy the spiral's arms.

[noun - organisms] The hypothesis that non-living matter can continuously give rise to biological organisms. The idea developed among ancient Greek philosophers, inspired by ideas of Anaximander (610–546 BCE) that humans had evolved from fish coming ultimately from the mud. It persisted for 24 centuries until finally laid to rest by experiments devised by Louis Pasteur (1822-1895 CE). Compare to abiogenesis.

• Appears in modules:

• Experimentation in Scientific Research

[noun - statistics] The variation within a dataset; the measure of how much individual values in a dataset differ from the mean, or average.

• Appears in modules:

• Biodiversity I
• Confidence Intervals
• Introduction to Descriptive Statistics
• Introduction to Inferential Statistics

[noun - environmental policy, human impacts on the environment, science & decision making] A person or group who has an interest in a resource, place, management decision, etc.

• Appears in modules:

• Craig Lee
• Sergio Avila

[noun - statistics] The standard deviation (σ) is a measure of the variability of values in a dataset. Standard deviation is one of the most common measures of statistical dispersion. If many data points are close to the mean of the dataset, the standard deviation is small; if many data points are far from the mean, then the standard deviation is large.

• Appears in modules:

• Confidence Intervals
• Introduction to Descriptive Statistics
• Introduction to Inferential Statistics
• Uncertainty, Error, and Confidence

[noun - statistics] The standard error of the mean is an inferential statistic that provides an estimate of how far the population mean is likely to be from the subsample mean. The standard error of the mean is calculated as the subsample standard deviation (s) divided by the square root of the subsample size (N), as seen in the following equation:

standard error of the mean = s/√N

• Appears in modules:

• Confidence Intervals

[noun - matter, physical & chemical properties, matter, thermodynamics] The common reference pressure condition for a gas. Standard pressure is 1 atm.

[noun - matter, physical & chemical properties, matter, thermodynamics] The common reference temperature condition for a gas. Standard temperature is 0°C (273.15 K).

[noun - statistics, data] In statistics, a statistic is a numerical value that represents a characteristic of a subsample selected from a larger statistical population. Contrast with parameter.

• Appears in modules:

• Confidence Intervals
• Introduction to Descriptive Statistics
• Introduction to Inferential Statistics
• Statistics in Science
• The Piltdown Hoax
• Uncertainty, Error, and Confidence

[noun - statistics] Also called random error, statistical error refers to the inherent variability of a measurement. Statistical error is caused by random fluctuations or natural variability within a system or of a measurement, and describes the precision of measurement. Compare to systematic error. See the module Uncertainty, Error, and Confidence.

• Appears in modules:

• Uncertainty, Error, and Confidence

[noun - statistics, data, research methods] Statistical significance provides a measure of the statistical probability for a result to have occurred and quantifies the likelihood that a result occurred by chance. Statistical significance does not define whether a difference or relationship is large or small, nor does it speak to the practical significance of an occurrence. The significance level (α) is reported as a percentage (10%, 5%, 1% ?), where the lower the level, the higher the probability that an occurrence was not due to chance. For more information, see the module Statistics in Science.

• Appears in modules:

• Comparison in Scientific Research
• Introduction to Inferential Statistics
• Statistics in Science

[noun] The mathematical study of data.

• Appears in modules:

• Confidence Intervals
• Population Genetics
• Statistics in Science
• The Piltdown Hoax

[noun] The existing state or condition.

• Appears in modules:

• Charles Darwin II

[person - rocks & minerals] Danish geologist and anatomist, born in Copenhagen (1638-1686). He was deeply interested in mineralogy, formulating the Law of Interfacial Angles. Steno was also appointed the Royal Anatomist for Denmark.

• Appears in modules:

• Defining Minerals

[person - atoms & subatomic particles, modern physics] German physicist and 1943 Nobel Prize winner in physics, noted for his work with Walther Gerlach in establishing the spin-quantization of electrons.

• Appears in modules:

• Atomic Theory III

[chemical reactions] The proportional relationship (ratio) between reactants and products in a chemical equation.

• Appears in modules:

• Stoichiometry
• Unit Conversion

[noun - organisms] A group of closely related organisms; a distinct variety, as in a strain of bacteria.

• Appears in modules:

• César Milstein
• DNA I
• DNA III
• Gene Expression
• Mendel and Independent Assortment
• Theories, Hypotheses, and Laws

[noun - atmospheric science] The layer of the atmosphere above the troposphere, where temperature increases with altitude because of the presence of the ozone layer. Only the highest clouds are within the stratosphere, but there is very little wind.

• Appears in modules:

• Composition of Earth's Atmosphere
• Factors that Control Regional Climate
• History of Earth's Atmosphere II
• Mario Molina

[acids, bases & pH] An acid that completely dissociates into its constituent ions in water.

• Appears in modules:

• Acids and Bases I
• Acids and Bases II

[acids, bases & pH] A base that completely dissociates into its constituent ions in water.

• Appears in modules:

• Acids and Bases II

[noun - statistics] A statistical test of significance for two subsamples. Student’s t-test is a method of statistical hypothesis testing that can be used to determine whether or not the difference between two subsamples is statistically significant.

• Appears in modules:

• Introduction to Inferential Statistics

[noun - seismology & plate tectonics] The process by which one tectonic plate moves beneath another.

• Appears in modules:

• History of Earth's Atmosphere I
• Origins of Plate Tectonic Theory
• Plates, Plate Boundaries, and Driving Forces
• The Carbon Cycle
• The Rock Cycle

[noun - seismology & plate tectonics] A region where one plate is being subducted beneath another, manifesting in a deep, linear trench, frequent earthquakes, and a chain of volcanoes. The western coast of South America is a subduction zone, as are the Marianas, the Phillippines, and the Aleutian Islands.

• Appears in modules:

• Plates, Plate Boundaries, and Driving Forces

[noun - research methods] A person or animal used in a research study.

• Appears in modules:

• Animal Behavior
• Barbara McClintock
• Bernardo Houssay
• Blood Biology I
• Bone Changes in Rock Climbers
• Comparison in Scientific Research
• Creativity in Science
• Data Analysis and Interpretation
• Ellen Ochoa
• Experimentation in Scientific Research
• Fabiola León-Velarde
• Mendel and Independent Assortment
• Peer Review in Scientific Publishing
• Scientific Controversy
• Scientific Ethics
• Scientists and the Scientific Community
• Statistics in Science
• The Phosphorus Cycle
• The Practice of Science
• The Process of Science
• The Scientific Method

[noun - statistics] Also commonly referred to as sample. In statistics, a subsample is a subset of a population. Because it is often impractical to study an entire population, a subset of the population may be observed to instead. This subsample may then be used to estimate characteristics of the entire population. For example, if a scientist is studying the beak sizes of finches in the Galapagos Islands, she could collect data for some of the finches (a subsample) to make generalizations about the entire population (all of the finches on the island).

• Appears in modules:

• Confidence Intervals
• Introduction to Descriptive Statistics
• Introduction to Inferential Statistics

[noun - atoms & subatomic particles, atoms & subatomic particles, modern physics] Subdivision of a shell in which the electron orbitals all have the same azimuthal quantum number, a valut that determines the physical, three-dimensional shape of the orbitals.

• Appears in modules:

• Atomic Theory IV

[noun - nutrition, compounds] A water-soluble crystalline carbohydrate. There are many types of sugar of varying degrees of sweetness, including fructose, which occurs naturally in fruit, and lactose, which occurs naturally in milk.

• Appears in modules:

• Bernardo Houssay
• Carbohydrates
• Carlos J. Finlay
• Cell Division II
• Chemical Equations
• Chemical Reactions
• Confidence Intervals
• Discovery and Structure of Cells
• DNA II
• Energy Metabolism I
• Fats and Proteins
• Gene Expression
• History of Earth's Atmosphere II
• Introduction to Inferential Statistics
• Measurement
• Membranes II
• Photosynthesis I
• Properties of Liquids
• Properties of Solids
• The Carbon Cycle

[noun - data, research methods] A very fast, powerful mainframe computer, used in advanced military and scientific applications.

• Appears in modules:

• Modeling in Scientific Research

[noun] The name of the fund established by the Comprehensive Environmental Response, Compensation and Liability Act (CERCLA) of 1980, which was enacted in the wake of the discovery of toxic waste dumps such as Love Canal and Times Beach in the 1970s. The fund is overseen by the U.S. Environmental Protection Agency (EPA) to clean up toxic waste sites and to compel responsible parties to perform cleanups or reimburse the government for sites remediated by EPA.

[noun] The outside or external part; the topside face of something.

• Appears in modules:

• Biodiversity I
• Blood Biology I
• Carbon Chemistry
• Carlos J. Finlay
• Composition of Earth's Atmosphere
• Confidence Intervals
• Craig Lee
• Data Analysis and Interpretation
• Defining Minerals
• Density
• Description in Scientific Research
• Earth Structure
• Energy
• Factors that Control Earth's Temperature
• Factors that Control Regional Climate
• Franklin Chang Díaz
• Gravity
• History of Earth's Atmosphere I
• Introduction to Paleoanthropology
• Kevin Arrigo
• Light and Electromagnetism
• Lipids
• Luis Walter Alvarez
• Mario Molina
• Membranes I
• Modeling in Scientific Research
• Origins of Life I
• Origins of Plate Tectonic Theory
• Photosynthesis I
• Plates, Plate Boundaries, and Driving Forces
• Properties of Liquids
• Properties of Minerals
• Properties of Solids
• Santiago Ramón y Cajal and Camillo Golgi
• Scientific Controversy
• Scientific Notation and Order of Magnitude
• Solutions, Solubility, and Colligative Properties
• States of Matter
• The Carbon Cycle
• The Hydrologic Cycle
• The Nature of Scientific Knowledge
• The Nitrogen Cycle
• The Phosphorus Cycle
• The Rock Cycle
• The Silicate Minerals
• Water
• Waves and Wave Motion

[noun - physical & chemical properties] The cohesive force exerted at the surface of a liquid that makes it tend to assume a spherical shape. Surface tension is related to the interactive forces between molecules of a liquid, and is caused by the fact that molecules at the surface are not surrounded by molecules on all sides. Consequently, they interact more strongly with those directly adjacent to them on the surface.

• Appears in modules:

• Properties of Liquids

[noun - matter, physical & chemical properties] A mixture in which insoluble particles are distributed in a liquid and will eventually separate. Non-homogenized milk and many types of salad dressing are examples of suspensions. Compare to colloid.

• Appears in modules:

• Properties of Liquids

[noun - anatomy & physiology, evolution & adaptation, organisms] The intimate living together of two dissimilar organisms in a mutually beneficial relationship.

• Appears in modules:

• Cellular Organelles I
• The Nitrogen Cycle

[noun] The production of a chemical compound by combining simpler compounds or elements.

• Appears in modules:

• Bernardo Houssay
• Cell Division I
• Cell Division II
• Cellular Organelles I
• Data Analysis and Interpretation
• David Ho
• Discovery and Structure of Cells
• DNA III
• Luis E. Miramontes
• Meselson and Stahl
• Origins of Life I
• Origins of Life II
• Percy Lavon Julian
• Photosynthesis I
• Y-Chromsome and Mitochondrial DNA Haplotypes

[adjective] Made by humans rather than found in nature; created through a chemical process; artificial.

• Appears in modules:

• Defining Minerals
• Luis E. Miramontes
• Membranes I
• Percy Lavon Julian
• Ruth Benerito
• The Nitrogen Cycle

[noun - research methods, scientific concepts] A group of interacting, interrelated or interdependent components that form a complex whole. The size of the system is defined for a given problem: In modeling, a system may be defined as the entire Earth or a single organism.

• Appears in modules:

• Absorption, Distribution, and Storage of Chemicals
• Adaptation
• Animal Behavior
• Atomic Theory I
• Atomic Theory II
• Atomic Theory III
• Atomic Theory IV
• Bernardo Houssay
• Biodiversity I
• Carbohydrates
• Carlos J. Finlay
• Cell Division I
• Cell Division II
• Cellular Organelles I
• César Milstein
• Charles Darwin I
• Chemical Equations
• Chemical Reactions
• Comparison in Scientific Research
• Data Analysis and Interpretation
• David Ho
• Defining Minerals
• Description in Scientific Research
• Diffusion I
• DNA I
• Early Ideas about Matter
• Ellen Ochoa
• Energy
• Energy Metabolism I
• Experimentation in Scientific Research
• Exponential Equations in Science II
• Fabiola León-Velarde
• Factors that Control Earth's Temperature
• Factors that Control Regional Climate
• Fats and Proteins
• France Anne-Dominic Córdova
• Franklin Chang Díaz
• Gene Expression
• Gravity
• History of Earth's Atmosphere I
• Kevin Arrigo
• Linear Equations in Science
• Luis Walter Alvarez
• Mario Molina
• Measurement
• Mendel and Inheritance
• Modeling in Scientific Research
• Origins of Plate Tectonic Theory
• Peer Review in Scientific Publishing
• Properties of Minerals
• Properties of Solids
• Santiago Ramón y Cajal and Camillo Golgi
• Scientific Controversy
• Scientific Ethics
• Scientific Notation and Order of Magnitude
• Sergio Avila
• States of Matter
• Statistics in Science
• Taxonomy I
• Taxonomy II
• Temperature
• The Hydrologic Cycle
• The Metric System
• The Mole and Atomic Mass
• The Nature of Scientific Knowledge
• The Nitrogen Cycle
• The Phosphorus Cycle
• The Practice of Science
• Theories, Hypotheses, and Laws
• Thermodynamics I
• Uncertainty, Error, and Confidence
• Understanding Scientific Journals and Articles
• Using Graphs and Visual Data in Science
• Wave Mathematics

[noun - statistics, research methods] Systematic error describes a bias or uncertainty in a measurement introduced by an instrumental, human, or environmental variable. Systematic error is due to an unknown but non-random fluctuation; however, if the source of a systematic error can be identified, it can often be eliminated or controlled. Systematic error affects the accuracy of a measurement. Compare to statistical error. See the module Uncertainty, Error, and Confidence.

• Appears in modules:

• Introduction to Inferential Statistics
• Statistics in Science
• Uncertainty, Error, and Confidence