Law has to do with rules and legal systems. If you live by the letter of the law, you follow society's guidelines to a T: you cross at the corner and always wait until the light is green.

A law is a rule that specifies what you can and can't do. Laws govern communities, countries, and even the world. Your town might have a leash law for dog owners, and international law prohibits throwing garbage off a boat. You can also refer to the police as "the law," as in "Don’t make me call the law." Law also refers to the entire legal system: We are all equal before the law (at least in theory).

Definitions of law

n the collection of rules imposed by authority

“civilization presupposes respect for the law
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administrative law
the body of rules and regulations and orders and decisions created by administrative agencies of government
canon law, ecclesiastical law
the body of codified laws governing the affairs of a Christian church
civil law
the body of laws established by a state or nation for its own regulation
case law, common law, precedent
a system of jurisprudence based on judicial precedents rather than statutory laws
international law, law of nations
the body of laws governing relations between nations
law of the land
a phrase used in the Magna Carta to refer to the then established law of the kingdom (as distinct from Roman or civil law); today it refers to fundamental principles of justice commensurate with due process
martial law
the body of law imposed by the military over civilian affairs (usually in time of war or civil crisis); overrides civil law
commercial law, law merchant, mercantile law
the body of rules applied to commercial transactions; derived from the practices of traders rather than from jurisprudence
military law
the body of laws and rules of conduct administered by military courts for the discipline, trial, and punishment of military personnel
Law of Moses, Mosaic law
the laws (beginning with the Ten Commandments) that God gave to the Israelites through Moses; it includes many rules of religious observance given in the first five books of the Old Testament (in Judaism these books are called the Torah)
Islamic law, sharia, sharia law, shariah, shariah law
the code of law derived from the Koran and from the teachings and example of Mohammed
statutory law
the body of laws created by legislative statutes
securities law
the body of laws governing the issuance and selling of securities
tax law
the body of laws governing taxation
case law, common law, precedent
(civil law) a law established by following earlier judicial decisions
legislation, statute law
law enacted by a legislative body
admiralty law, marine law, maritime law
the branch of international law that deals with territorial and international waters or with shipping or with ocean fishery etc.
hudood, hudud
Islamic laws stating the limits ordained by Allah and including the deterrent punishments for serious crimes
Type of:
accumulation, aggregation, assemblage, collection
several things grouped together or considered as a whole

n legal document setting forth rules governing a particular kind of activity

“there is a law against kidnapping”
Constitution of the United States
the constitution written at the Constitutional Convention in Philadelphia in 1787 and subsequently ratified by the original thirteen states
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anti-drug law
a law forbidding the sale or use of narcotic drugs
RICO, RICO Act, Racketeer Influenced and Corrupt Organizations Act, anti-racketeering law
law intended to eradicate organized crime by establishing strong sanctions and forfeiture provisions
antitrust law, antitrust legislation
law intended to promote free competition in the market place by outlawing monopolies
statute of limitations
a statute prescribing the time period during which legal action can be taken
constitution, fundamental law, organic law
law determining the fundamental political principles of a government
public law
a law affecting the public at large
blue law
a statute regulating work on Sundays
blue sky law
a state law regulating the sale of securities in an attempt to control the sale of securities in fraudulent enterprises
gag law
any law that limits freedom of the press
homestead law
a law conferring privileges on owners of homesteads
poor law
a law providing support for the poor
Riot Act
a former English law requiring mobs to disperse after a magistrate reads the law to them
a law forbidding the sale of alcoholic beverages
Type of:
instrument, legal document, legal instrument, official document
(law) a document that states some contractual relationship or grants some right

n a rule or body of rules of conduct inherent in human nature and essential to or binding upon human society

natural law
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divine law
a law that is believed to come directly from God
a basic truth or law or assumption
sound law
a law describing sound changes in the history of a language
a guiding principle
basic principle, basics, bedrock, fundamental principle, fundamentals
principles from which other truths can be derived
the principles that guide reasoning within a given field or situation
pleasure principle, pleasure-pain principle, pleasure-unpleasure principle
(psychoanalysis) the governing principle of the id; the principle that an infant seeks gratification and fails to distinguish fantasy from reality
reality principle
(psychoanalysis) the governing principle of the ego; the principle that as a child grows it becomes aware of the real environment and the need to accommodate to it
the principle of revolt against constituted authority
(physics) the maintenance of a certain quantities unchanged during chemical reactions or physical transformations
Grimm's law
a sound law relating German consonants and consonants in other Indo-European languages
Verner's law
a qualification of Grimm's law
the ultimate principle of the universe
Type of:
concept, conception, construct
an abstract or general idea inferred or derived from specific instances

n a generalization that describes recurring facts or events in nature

“the laws of thermodynamics”
law of nature
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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
principle, rule
a rule or law concerning a natural phenomenon or the function of a complex system
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
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
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
Benford's law
a law used by auditors to identify fictitious populations of numbers; applies to any population of numbers derived from other numbers
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)
Boyle's law, Mariotte's law
the pressure of an ideal gas at constant temperature varies inversely with the volume
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
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
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
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
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
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)
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
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
Hooke's law
(physics) the principle that (within the elastic limit) the stress applied to a solid is proportional to the strain produced
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
Kepler's law, Kepler's law of planetary motion
(astronomy) one of three empirical laws of planetary motion stated by Johannes Kepler
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
law of averages
a law affirming that in the long run probabilities will determine performance
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
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
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
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
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
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
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
law of thermodynamics
(physics) a law governing the relations between states of energy in a closed system
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
Newton's law, Newton's law of motion, law of motion
one of three basic laws of classical mechanics
Ohm's law
electric current is directly proportional to voltage and inversely proportional to resistance; I = E/R
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
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
Mendeleev's law, periodic law
(chemistry) the principle that chemical properties of the elements are periodic functions of their atomic numbers
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
Planck's radiation law
(physics) an equation that expresses the distribution of energy in the radiated spectrum of an ideal black body
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
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
Weber's law
(psychophysics) the concept that a just-noticeable difference in a stimulus is proportional to the magnitude of the original stimulus
Boltzmann distribution law, Maxwell-Boltzmann distribution law
(physics) a law expressing the distribution of energy among the molecules of a gas in thermal equilibrium
Gestalt law of organization, Gestalt principle of organization
a principle of Gestalt psychology that identifies factors leading to particular forms of perceptual organization
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
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
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
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
third law of thermodynamics
law stating that the entropy of a substance approaches zero as its temperature approaches absolute zero
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
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
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
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
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
mass-energy equivalence
(physics) the principle that a measured quantity of mass is equivalent (according to relativity theory) to a measured quantity of energy
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
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
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
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
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
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
principle of liquid displacement
(hydrostatics) the volume of a body immersed in a fluid is equal to the volume of the displaced fluid
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
principle of superposition, superposition, superposition principle
(geology) the principle that in a series of stratified sedimentary rocks the lowest stratum is the oldest
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
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
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
Type of:
concept, conception, construct
an abstract or general idea inferred or derived from specific instances

n the learned profession that is mastered by graduate study in a law school and that is responsible for the judicial system

“he studied law at Yale”
practice of law
Type of:
learned profession
one of the three professions traditionally believed to require advanced learning and high principles

n the branch of philosophy concerned with the law and the principles that lead courts to make the decisions they do

jurisprudence, legal philosophy
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contract law
that branch of jurisprudence that studies the rights and obligations of parties entering into contracts
corporation law
that branch of jurisprudence that studies the laws governing corporations
matrimonial law
that branch of jurisprudence that studies the laws governing matrimony
patent law
that branch of jurisprudence that studies the laws governing patents
Type of:
the rational investigation of questions about existence and knowledge and ethics

n the force of policemen and officers

“the law came looking for him”
constabulary, police, police force
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European Law Enforcement Organisation, Europol
police organization for the European Union; aims to improve effectiveness and cooperation among European police forces
gendarmerie, gendarmery
French police force; a group of gendarmes or gendarmes collectively
Mutawa, Mutawa'een
religious police in Saudi Arabia whose duty is to ensure strict adherence to established codes of conduct; offenders may be detained indefinitely; foreigners are not excluded
Mounties, RCMP, Royal Canadian Mounted Police
the federal police force of Canada
New Scotland Yard, Scotland Yard
the detective department of the metropolitan police force of London
secret police
a police force that operates in secrecy (usually against persons suspected of treason or sedition)
SS, Schutzstaffel
special police force in Nazi Germany founded as a personal bodyguard for Adolf Hitler in 1925; the SS administered the concentration camps
posse, posse comitatus
a temporary police force
the secret state police in Nazi Germany; known for its terrorist methods
Type of:
force, personnel
group of people willing to obey orders
law enforcement agency
an agency responsible for insuring obedience to the laws

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