- Types:
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all-or-none law
(neurophysiology) a nerve impulse resulting from a weak stimulus is just as strong as a nerve impulse resulting from a strong stimulus
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principle, rule
a rule or law concerning a natural phenomenon or the function of a complex system
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Archimedes' principle, law of Archimedes
(hydrostatics) the apparent loss in weight of a body immersed in a fluid is equal to the weight of the displaced fluid
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Avogadro's hypothesis, Avogadro's law
the principle that equal volumes of all gases (given the same temperature and pressure) contain equal numbers of molecules
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Bernoulli's law, law of large numbers
(statistics) law stating that a large number of items taken at random from a population will (on the average) have the population statistics
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Benford's law
a law used by auditors to identify fictitious populations of numbers; applies to any population of numbers derived from other numbers
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Bose-Einstein statistics
(physics) statistical law obeyed by a system of particles whose wave function is not changed when two particles are interchanged (the Pauli exclusion principle does not apply)
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Boyle's law, Mariotte's law
the pressure of an ideal gas at constant temperature varies inversely with the volume
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Coulomb's Law
a fundamental principle of electrostatics; the force of attraction or repulsion between two charged particles is directly proportional to the product of the charges and inversely proportional to the distance between them; principle also holds for magnetic poles
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Dalton's law, Dalton's law of partial pressures, law of partial pressures
(chemistry and physics) law stating that the pressure exerted by a mixture of gases equals the sum of the partial pressures of the gases in the mixture; the pressure of a gas in a mixture equals the pressure it would exert if it occupied the same volume alone at the same temperature
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distribution law
(chemistry) the total energy in an assembly of molecules is not distributed equally but is distributed around an average value according to a statistical distribution
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equilibrium law, law of chemical equilibrium
(chemistry) the principle that (at chemical equilibrium) in a reversible reaction the ratio of the rate of the forward reaction to the rate of the reverse reaction is a constant for that reaction
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Fechner's law, Weber-Fechner law
(psychophysics) the concept that the magnitude of a subjective sensation increases proportional to the logarithm of the stimulus intensity; based on early work by E. H. Weber
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Fermi-Dirac statistics
(physics) law obeyed by a systems of particles whose wave function changes when two particles are interchanged (the Pauli exclusion principle applies)
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Charles's law, Gay-Lussac's law, law of volumes
(physics) the density of an ideal gas at constant pressure varies inversely with the temperature
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Henry's law
(chemistry) law formulated by the English chemist William Henry; the amount of a gas that will be absorbed by water increases as the gas pressure increases
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Hooke's law
(physics) the principle that (within the elastic limit) the stress applied to a solid is proportional to the strain produced
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Hubble law, Hubble's law
(astronomy) the generalization that the speed of recession of distant galaxies (the red shift) is proportional to their distance from the observer
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Kepler's law, Kepler's law of planetary motion
(astronomy) one of three empirical laws of planetary motion stated by Johannes Kepler
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Kirchhoff's laws
(physics) two laws governing electric networks in which steady currents flow: the sum of all the currents at a point is zero and the sum of the voltage gains and drops around any closed circuit is zero
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law of averages
a law affirming that in the long run probabilities will determine performance
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law of constant proportion, law of definite proportions
(chemistry) law stating that every pure substance always contains the same elements combined in the same proportions by weight
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law of diminishing returns
a law affirming that to continue after a certain level of performance has been reached will result in a decline in effectiveness
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law of effect
(psychology) the principle that behaviors are selected by their consequences; behavior having good consequences tends to be repeated whereas behavior that leads to bad consequences is not repeated
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law of equivalent proportions, law of reciprocal proportions
(chemistry) law stating that the proportions in which two elements separately combine with a third element are also the proportions in which they combine together
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Newton's law of gravitation, law of gravitation
(physics) the law that states any two bodies attract each other with a force that is directly proportional to the product of their masses and inversely proportional to the square of the distance between them
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Dalton's law, law of multiple proportions
(chemistry) law stating that when two elements can combine to form more than one compound the amounts of one of them that combines with a fixed amount of the other will exhibit a simple multiple relation
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law of mass action
(chemistry) the law that states the following principle: the rate of a chemical reaction is directly proportional to the molecular concentrations of the reacting substances
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law of thermodynamics
(physics) a law governing the relations between states of energy in a closed system
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Mendel's law
(genetics) one of two principles of heredity formulated by Gregor Mendel on the basis of his experiments with plants; the principles were limited and modified by subsequent genetic research
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Newton's law, Newton's law of motion, law of motion
one of three basic laws of classical mechanics
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Ohm's law
electric current is directly proportional to voltage and inversely proportional to resistance; I = E/R
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Pascal's law, Pascal's law of fluid pressures
pressure applied anywhere to a body of fluid causes a force to be transmitted equally in all directions; the force acts at right angles to any surface in contact with the fluid
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Pauli exclusion principle, exclusion principle
no two electrons or protons or neutrons in a given system can be in states characterized by the same set of quantum numbers
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Mendeleev's law, periodic law
(chemistry) the principle that chemical properties of the elements are periodic functions of their atomic numbers
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Planck's law
(physics) the basis of quantum theory; the energy of electromagnetic waves is contained in indivisible quanta that have to be radiated or absorbed as a whole; the magnitude is proportional to frequency where the constant of proportionality is given by Planck's constant
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Planck's radiation law
(physics) an equation that expresses the distribution of energy in the radiated spectrum of an ideal black body
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principle of relativity
(physics) a universal law that states that the laws of mechanics are not affected by a uniform rectilinear motion of the system of coordinates to which they are referred
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Stevens' law, Stevens' power law, power law
(psychophysics) the concept that the magnitude of a subjective sensation increases proportional to a power of the stimulus intensity
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Weber's law
(psychophysics) the concept that a just-noticeable difference in a stimulus is proportional to the magnitude of the original stimulus
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Boltzmann distribution law, Maxwell-Boltzmann distribution law
(physics) a law expressing the distribution of energy among the molecules of a gas in thermal equilibrium
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Gestalt law of organization, Gestalt principle of organization
a principle of Gestalt psychology that identifies factors leading to particular forms of perceptual organization
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Kepler's first law
a law stating that the orbit of each planet is an ellipse with the sun at one focus of the ellipse
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Kepler's second law, law of areas, law of equal areas
a law concerning the speed at which planets travel; a line connecting a planet to the sun will sweep out equal areas in equal times
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Kepler's third law, harmonic law
a law stating that the ratio of the square of the revolutionary period (in years) to the cube of the orbital axis (in astronomical units) is the same for all planets
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second law of thermodynamics
a law stating that mechanical work can be derived from a body only when that body interacts with another at a lower temperature; any spontaneous process results in an increase of entropy
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third law of thermodynamics
law stating that the entropy of a substance approaches zero as its temperature approaches absolute zero
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zeroth law of thermodynamics
the law that if two bodies are in thermal equilibrium with a third body then the first two bodies are in thermal equilibrium with each other
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Le Chatelier principle, Le Chatelier's law, Le Chatelier's principle, Le Chatelier-Braun principle
the principle that if any change is imposed on a system that is in equilibrium then the system tends to adjust to a new equilibrium counteracting the change
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Gresham's Law
(economics) the principle that when two kinds of money having the same denominational value are in circulation the intrinsically more valuable money will be hoarded and the money of lower intrinsic value will circulate more freely until the intrinsically more valuable money is driven out of circulation; bad money drives out good; credited to Sir Thomas Gresham
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law of segregation
members of a pair of homologous chromosomes separate during the formation of gametes and are distributed to different gametes so that every gamete receives only one member of the pair
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law of independent assortment
each member of a pair of homologous chromosomes separates independently of the members of other pairs so the results are random
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mass-energy equivalence
(physics) the principle that a measured quantity of mass is equivalent (according to relativity theory) to a measured quantity of energy
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Naegele's rule
rule for calculating an expected delivery date; subtract three months from the first day of the last menstrual period and add seven days to that date
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Newton's first law, Newton's first law of motion, first law of motion
a body remains at rest or in motion with a constant velocity unless acted upon by an external force
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Newton's second law, Newton's second law of motion, second law of motion
the rate of change of momentum is proportional to the imposed force and goes in the direction of the force
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Newton's third law, Newton's third law of motion, law of action and reaction, third law of motion
action and reaction are equal and opposite
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Occam's Razor, Ockham's Razor, law of parsimony, principle of parsimony
the principle that entities should not be multiplied needlessly; the simplest of two competing theories is to be preferred
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principle of equivalence
(physics) the principle that an observer has no way of distinguishing whether his laboratory is in a uniform gravitational field or is in an accelerated frame of reference
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principle of liquid displacement
(hydrostatics) the volume of a body immersed in a fluid is equal to the volume of the displaced fluid
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Huygens' principle of superposition, principle of superposition
the displacement of any point due to the superposition of wave systems is equal to the sum of the displacements of the individual waves at that point
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principle of superposition, superposition, superposition principle
(geology) the principle that in a series of stratified sedimentary rocks the lowest stratum is the oldest
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mass action, mass-action principle
(neurology) the principle that the cortex of the brain operates as a coordinated system with large masses of neural tissue involved in all complex functioning
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localisation, localisation of function, localisation principle, localization, localization of function, localization principle
(physiology) the principle that specific functions have relatively circumscribed locations in some particular part or organ of the body
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conservation of energy, first law of thermodynamics, law of conservation of energy
the fundamental principle of physics that the total energy of an isolated system is constant despite internal changes