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anything that has massmass,
in physics, the quantity of matter in a body regardless of its volume or of any forces acting on it. The term should not be confused with weight, which is the measure of the force of gravity (see gravitation) acting on a body.
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 and occupies space. Matter is sometimes called koinomatter (Gr. koinos=common) to distinguish it from antimatter, or matter composed of antiparticlesantiparticle,
elementary particle corresponding to an ordinary particle such as the proton, neutron, or electron, but having the opposite electrical charge and magnetic moment.
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The Properties of Matter

The general properties of matter result from its relationship with mass and space. Because of its mass, all matter has inertiainertia
, in physics, the resistance of a body to any alteration in its state of motion, i.e., the resistance of a body at rest to being set in motion or of a body in motion to any change of speed or change in direction of motion. Inertia is a property common to all matter.
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 (the mass being the measure of its inertia) and weightweight,
measure of the force of gravity on a body (see gravitation). Since the weights of different bodies at the same location are proportional to their masses, weight is often used as a measure of mass.
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, if it is in a gravitational field (see gravitationgravitation,
the attractive force existing between any two particles of matter. The Law of Universal Gravitation

Since the gravitational force is experienced by all matter in the universe, from the largest galaxies down to the smallest particles, it is often called
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). Because it occupies space, all matter has volume and impenetrability, since two objects cannot occupy the same space simultaneously.

The special properties of matter, on the other hand, depend on internal structure and thus differ from one form of matter, i.e., one substance, to another. Such properties include ductilityductility,
ability of a metal to plastically deform without breaking or fracturing, with the cohesion between the molecules remaining sufficient to hold them together (see adhesion and cohesion). Ductility is important in wire drawing and sheet stamping.
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, elasticityelasticity,
the ability of a body to resist a distorting influence or stress and to return to its original size and shape when the stress is removed. All solids are elastic for small enough deformations or strains, but if the stress exceeds a certain amount known as the elastic
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, hardnesshardness,
property of matter commonly described as the resistance of a substance to being scratched by another substance. The degree of hardness is relative, different substances being compared with one another.
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, malleabilitymalleability,
property of a metal describing the ease with which it can be hammered, forged, pressed, or rolled into thin sheets. Metals vary in this respect; pure gold is the most malleable. Silver, copper, aluminum, lead, tin, zinc, and iron are also very malleable.
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, porosity (ability to permit another substance to flow through it), and tenacity (resistance to being pulled apart).

The States of Matter

Matter is ordinarily observed in three different states, or phases (see states of matterstates of matter,
forms of matter differing in several properties because of differences in the motions and forces of the molecules (or atoms, ions, or elementary particles) of which they are composed.
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), although scientists distinguish three additional states. Matter in the solid state has both a definite volume and a definite shape; matter in the liquid state has a definite volume but no definite shape, assuming the shape of whatever container it is placed in; matter in the gaseous state has neither a definite volume nor a definite shape and expands to fill any container. The properties of a plasmaplasma,
in physics, fully ionized gas of low density, containing approximately equal numbers of positive and negative ions (see electron and ion). It is electrically conductive and is affected by magnetic fields.
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, or extremely hot, ionized gas, are sufficiently different from those of a gas at ordinary temperatures for scientists to consider them to be the fourth state of matter. So too are the properties of the Bose-Einstein and fermionic condensatescondensate,
matter in the form of a gas of atoms, molecules, or elementary particles that have been so chilled that their motion is virtually halted and as a consequence they lose their separate identities and merge into a single entity.
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, which exist only at temperatures approximating absolute zero (−273.15°C;), and they are considered the fifth and sixth states of matter respectively.

Early Theories of Matter

In ancient times various theories were suggested about the nature of matter. Empedocles held that all matter is made up of four "elements"—earth, air, fire, and water. Leucippus and his pupil Democritus proposed an atomic basis of matter, believing that all matter is built up from tiny particles differing in size and shape. Anaxagoras, however, rejected any theory in which matter is viewed as composed of smaller constituents, whether atoms or elements, and held instead that matter is continuous throughout, being entirely of a single substance.

Modern Theory of Matter

The modern theory of matter dates from the work of John Dalton at the beginning of the 19th cent. The atomatom
[Gr.,=uncuttable (indivisible)], basic unit of matter; more properly, the smallest unit of a chemical element having the properties of that element. Structure of the Atom
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 is considered the basic unit of any element, and atoms may combine chemically to form molecules, the moleculemolecule
[New Lat.,=little mass], smallest particle of a compound that has all the chemical properties of that compound. A single atom is usually not referred to as a molecule, and ionic compounds such as common salt are not made up of molecules.
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 being the smallest unit of any substance that possesses the properties of that substance. An elementelement,
in chemistry, a substance that cannot be decomposed into simpler substances by chemical means. A substance such as a compound can be decomposed into its constituent elements by means of a chemical reaction, but no further simplification can be achieved.
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 in modern theory is any substance all of whose atoms are the same (i.e., have the same atomic numberatomic number,
often represented by the symbol Z, the number of protons in the nucleus of an atom, as well as the number of electrons in the neutral atom. Atoms with the same atomic number make up a chemical element. Atomic numbers were first assigned to the elements c.
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), while a compound is composed of different types of atoms together in molecules.

Physical and Chemical Changes

The difference between a mixture and a compound helps to illustrate the difference between a physical change and a chemical change. Different atoms may also be present together in a mixture, but in a mixture they are not bound together chemically as they are in a compound. In a physical change, such as a change of state (e.g., from solid to liquid), the substance as a whole changes, but its underlying structure remains the same; water is still composed of molecules containing two hydrogen atoms and one oxygen atom whether it is in the form of ice, liquid water, or steam. In a chemical change, however, the substance participates in a chemical reactionchemical reaction,
process by which one or more substances may be transformed into one or more new substances. Energy is released or is absorbed, but no loss in total molecular weight occurs.
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, with a consequent reordering of its atoms. As a result, it becomes a different substance with a different set of properties.

Many of the physical properties and much of the behavior of matter can be understood without detailed assumptions about the structure of atoms and molecules. For example, the kinetic-molecular theory of gaseskinetic-molecular theory of gases,
physical theory that explains the behavior of gases on the basis of the following assumptions: (1) Any gas is composed of a very large number of very tiny particles called molecules; (2) The molecules are very far apart compared to their sizes,
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 provides a good explanation of the nature of temperaturetemperature,
measure of the relative warmth or coolness of an object. Temperature is measured by means of a thermometer or other instrument having a scale calibrated in units called degrees. The size of a degree depends on the particular temperature scale being used.
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 and the basis of the various gas lawsgas laws,
physical laws describing the behavior of a gas under various conditions of pressure, volume, and temperature. Experimental results indicate that all real gases behave in approximately the same manner, having their volume reduced by about the same proportion of the
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 and also gives insight into the different states of matter. Substances in different states vary in the strength of the forces between their molecules, with intermolecular forces being strongest in solids and weakest in gases. The force holding like molecules together is called cohesion, while that between unlike molecules is called adhesion (see adhesion and cohesionadhesion and cohesion,
attractive forces between material bodies. A distinction is usually made between an adhesive force, which acts to hold two separate bodies together (or to stick one body to another) and a cohesive force, which acts to hold together the like or unlike
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). Among the phenomena resulting from intermolecular forces are surface tensionsurface tension,
tendency of liquids to reduce their exposed surface to the smallest possible area. A drop of water, for example, tends to assume the shape of a sphere. The phenomenon is attributed to cohesion, the attractive forces acting between the molecules of the liquid
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 and capillaritycapillarity
or capillary action,
phenomenon in which the surface of a liquid is observed to be elevated or depressed where it comes into contact with a solid. For example, the surface of water in a clean drinking glass is seen to be slightly higher at the edges, where
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. An even larger number of aspects of matter can be understood when the nature and structure of the atom are taken into account. The quantum theoryquantum theory,
modern physical theory concerned with the emission and absorption of energy by matter and with the motion of material particles; the quantum theory and the theory of relativity together form the theoretical basis of modern physics.
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 has provided the key to understanding the atom, and most basic problems relating to the atom have been solved.

The Relationship of Matter and Energy

The atomic theory of matter does not answer the question of the basic nature of matter. It is now known that matter and energy are intimately related. According to the law of mass-energy equivalence, developed by Albert Einstein as part of his theory of relativityrelativity,
physical theory, introduced by Albert Einstein, that discards the concept of absolute motion and instead treats only relative motion between two systems or frames of reference.
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, a quantity of matter of mass m possesses an intrinsic rest mass energy E given by E = mc2, where c is the speed of light. This equivalence is dramatically demonstrated in the phenomena of nuclear fission and fusion (see nuclear energynuclear energy,
the energy stored in the nucleus of an atom and released through fission, fusion, or radioactivity. In these processes a small amount of mass is converted to energy according to the relationship E = mc2, where E is energy, m
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; nucleusnucleus,
in physics, the extremely dense central core of an atom. The Nature of the Nucleus

Atomic nuclei are composed of two types of particles, protons and neutrons, which are collectively known as nucleons.
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), in which a small amount of matter is converted to a rather large amount of energy. The converse reaction, the conversion of energy to matter, has been observed frequently in the creation of many new elementary particleselementary particles,
the most basic physical constituents of the universe. Basic Constituents of Matter

Molecules are built up from the atom, which is the basic unit of any chemical element. The atom in turn is made from the proton, neutron, and electron.
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. The study of elementary particles has not solved the question of the nature of matter but only shifted it to a smaller scale.


See V. H. Booth, Elements of Physical Science: The Nature of Matter and Energy (1970); G. Amaldi, The Nature of Matter: Physical Theory from Thales to Fermi (1982).

Matter (physics)

A term that traditionally refers to the substance of which all bodies consist. Matter in classical mechanics is closely identified with mass. Modern analyses distinguish two types of mass: inertial mass, by which matter retains its state of rest or uniform rectilinear motion in the absence of external forces; and gravitational mass, by which a body exerts forces of attraction on other bodies, and by which it reacts to those forces. Expressed in appropriate units, these two properties are numerically equal—a purely experimental fact, unexplained by theory. Albert Einstein made the equality of inertial and gravitational mass a fundamental principle (principle of equivalence), as one of the two postulates of the theory of general relativity. See Gravitation, Inertia, Mass, Relativity, Weight

In quantum mechanics, mass is only one among many properties (quantum numbers) that a particle can have, for example, electric charge, spin, and parity. The nearest quantum-mechanical analogs of traditional matter are fermions, having half-integral values of spin. Forces are mediated by exchange of bosons, particles having integral spins. Fermions correspond to classical matter in exhibiting impenetrability (a consequence of the exclusion principle), but the correspondence is only rough. For example, fermions can also be exchanged in interactions (a photon and an electron can exchange an electron), and they also exhibit wavelike (nonlocalized) behavior. States of classical matter-particles were given by their positions and momenta, but in quantum mechanics it is impossible to assign simultaneous precise positions and momenta to particles. See Exclusion principle, Quantum electrodynamics, Quantum mechanics, Quantum statistics

The primary constituents of ordinary matter are baryonic, consisting of quarks. However it is possible that as much as 99% (by mass) of the matter in the universe consists of nonbaryonic “dark matter” whose nature is yet to be discovered. See Baryon, Quarks



“a philosophical category denoting the objective reality which is given to man by his sensations and which is copied, photographed, and reflected by our sensations, while existing independently of them” (V. I. Lenin, Poln. sobr. soch., 5th ed., vol. 18, p. 131). Matter is the infinite multitude of all the objects and systems in the world and the substratum of all properties, connections, relations, and forms of motion. Matter comprises not only all directly observable natural objects and bodies, but also all those which in principle will be known in the future with improvement of the means of observation and experiment. The entire world around us is moving matter in its infinitely diverse forms and manifestations and with all its properties, connections, and relations. The Marxist-Leninist conception of matter is organically related to the dialectical materialist answer to the basic question of philosophy. This conception is based on the principle of the material unity of the world and the primacy of matter over human consciousness and on the principle of the knowability of the world through the consistent study of matter’s specific properties, connections, and forms of motion.

In pre-Marxist philosophy and natural science, matter as a philosophical category was often identified with specific types of matter, such as physical substance or the atoms of chemical compounds, or with such properties of matter as mass, which was regarded as a measure of the quantity of matter. In reality, physical substance encompasses not all matter, but only those objects and systems that have a non-zero rest mass. There also exist types of matter that have no rest mass: the electromagnetic field and its quanta (photons), the gravitational field, and neutrinos.

The reduction of matter as objective reality to particular states and properties of matter provoked crises in the history of science, as was the case in the late 19th and early 20th centuries, when the identification of matter with indivisible atoms and material substance was shown to be invalid, and some idealistically minded physicists concluded that “matter has disappeared,” “materialism has now been refuted,” and so on. These conclusions were erroneous, but further elaboration of the dialectical materialist conception of matter and its basic properties was required to overcome the methodological crisis in physics.

The term “antimatter,” denoting various antiparticles, such as antiprotons, antineutrons, and positrons, and the micro- and macro-systems composed of them, is frequently encountered. This term is not precise, for in actuality all these entities are particular types of matter, antiparticles of material substance, or antisubstance. The world may contain a multitude of other, as yet unknown types of matter with extraordinary specific properties, but they are all elements of the objective reality that exists independently of consciousness.

In pre-Marxist materialism, matter was often defined as the substance (foundation) of all things and phenomena, a view that opposed the idealist religious conception of the world, which interpreted substance as god’s will, the absolute spirit, or human consciousness, which was separated from the brain, made absolute, and deified. At the same time material substance was often construed as prime matter and reduced to primary and structureless elements that were identified with indivisible atoms. It was believed that while various objects and material formations can arise and disappear, substance cannot be created or destroyed and is always stable in its essence. Change occurs only in the specific forms of its existence, in the quantitative combinations and relative positions of the elements.

In modern science the concept of substance has undergone radical change. Dialectical materialism recognizes the substantiality of matter, but only in a restricted sense, as it relates to the materialist solution of the basic problem of philosophy and to the revelation of the nature of various properties and forms of the motion of bodies. Matter and not consciousness or an imaginary divine spirit is the substance of all properties, relations, and forms of motion that exist in the world and the ultimate basis of all spiritual phenomena. No property or form of motion can exist in and of itself; it is always inherent in a specific material formation, which is its substratum. In this sense the concept of substance is also equivalent to the concept of the material substratum of various processes and phenomena. Recognition of the substantiality and absolute nature of matter is also equivalent to the principle of the material unity of the world, which is confirmed by the entire historical development of science and practice.

However, it is important to take into account the fact that matter itself exists only as an infinite diversity of specific formations and systems. In the structure of each of these specific forms of matter there is no primary, structureless, and immutable substance underlying all properties of matter. Every material object has an inexhaustible diversity of structural connections and is capable of internal changes and transformations into qualitatively different forms of matter. “The ’essence’ of things, or ’substance,’ “wrote Lenin, “is also relative; it expresses only the degree of profundity of man’s knowledge of objects; and while yesterday the profundity of this knowledge did not go beyond the atom, and today does not go beyond the electron and ether, dialectical materialism insists on the temporary, relative, approximate character of all these milestones in the knowledge of nature gained by the progressing science of man. The electron is as inexhaustible as the atom, nature is infinite” (ibid., p. 277).

Nevertheless, it is always important for the progress of scientific knowledge and for refuting various idealist concepts to show the material substratum that underlies the phenomena, properties, and forms of motion of the objective world that are studied at a particular time. Thus the revelation of the substratum of thermal, electrical, magnetic, and optical processes and of various chemical reactions was of great importance historically, for it led to the development of the theory of the atomic structure of matter, the theory of the electromagnetic field, and quantum mechanics. Today, science faces such tasks as revealing the structure of elementary particles and studying in greater depth the material foundations of heredity and the nature of consciousness. The fulfillment of these tasks will advance human knowledge to encompass new, deeper structural levels of matter. “Human thought goes endlessly deeper from appearance to essence, from essence of the first order, as it were, to essence of the second order, and so on without end” (ibid., vol. 29, p. 227).

Material objects always have internal order and systemic organization. Order is manifested in the regular motion and interaction of all elements of matter, through which they are united into systems. A system is an internally ordered set of interconnected elements. The relation among elements in a system is more stable, essential, and internally necessary than the relation of each of the elements to the environment and to elements of other systems. Man’s knowledge of the structural organization of matter is relative and changeable, depending on the constantly expanding possibilities of experiments, observations, and scientific theories. But it makes specific and supplements the philosophical conception of matter as objective reality.

Modern science recognizes the following types of material systems and corresponding structural levels of matter: elementary particles and fields (such as the electromagnetic and gravitational fields), atoms, molecules and macroscopic bodies of various dimensions, geological systems, the earth and other planets, stars, intragalactic systems (such as diffuse nebulas and star clusters), the Milky Way Galaxy, systems of galaxies, and the metagalaxy, whose boundaries and structure have not yet been established. The current boundaries of knowledge of the structure of matter extend from 10-14 cm to 1028 cm (approximately 13 billion light-years), but even within this range there may exist a multitude of as yet unknown types of matter. Such objects as quasars and pulsars were discovered in the 1960’s.

Animate matter and socially organized matter thus far are known to exist only on earth. Their appearance was the result of the natural and law-governed self-development of matter, which is just as inseparable from its existence as motion, the quality of structure, and other properties. Animate matter is the entire aggregate of organisms capable of reproduction and the transfer and accumulation of genetic information in the course of evolution. Socially organized matter is the highest form of development of life—an aggregate including both individuals having the capacity to think and consciously transform reality and also communities of various levels. These types of matter also have a systemic organization. The structure of social systems also includes various technical material systems that have been created by man to achieve set goals.

At each stage of cognition it would have been incorrect to identify the philosophical conception of matter as objective reality with the specific scientific concepts of its structure and forms, for in that event all as yet unknown but existing objects and systems would have been excluded from the structure of matter. This is inaccurate and contradicts the principle of the material unity of the world, a unity that has a multitude of specific manifestations revealed by science and practice. This unity is manifested in the universal connection and mutual conditioning of objects and phenomena, in the possibility of mutual conversion of forms of moving matter into other forms, in the relation and mutual conversion of types of motion and energy, and in the historical development of nature and the emergence of more complex forms of matter and motion from relatively less complex ones. The material unity of the world is also manifested in the interconnection of all structural levels of matter and in the interdependence of the phenomena of the microcosm and macrocosm. This unity is also reflected in the fact that matter has a set of universal properties and dialectical laws governing structural organization, change, and development. Among the universal properties of matter are its inability to be created or destroyed, its eternal existence in time and infiniteness in space, and the inexhaustibility of its structure. Motion, change, and law-governed self-development, manifested in various forms, and the conversion of states into other states are always inherent in matter.

Space and time are universal forms of the existence of matter that do not exist apart from it, just as material objects without spatial and temporal properties could not exist. A universal property of matter is the determinacy of all phenomena and their dependence on structural relations in material systems, on external factors, and on the causes and conditions that give rise to them. Interaction leads to the mutual change of bodies (or of their states) and to their reflection of each other. Reflection, which is manifested in all processes, depends on the structure of the interacting systems and on the character of external influences. The historical development of the property of reflection leads, in the course of the evolution of animate nature and society, to the appearance of its highest form—abstract and constantly perfectible thought—by means of which matter comes, as it were, to a realization of the laws governing its own existence and to its own goal-directed change. The universal properties of matter are also manifested in the universal laws of its existence and development: the law of the unity and struggle of opposites, the mutual transitions of quantitative and qualitative changes, the law of causality, and other very important aspects of material existence revealed by dialectical materialism and all modern science.


Engels, F. “Anti-Dühring, otd. pervyi.” In K. Marx and F. Engels, Soch., 2nd ed., vol. 20.
Engels, F. “Dialektika prirody.” Ibid.
Lenin, V. I. “Materializm i empiriokrititsizm.” Poln. sobr. soch., 5th ed., vol. 18.
Lenin, V. I. “Karl Marks.” Ibid., vol. 26.
Arkhiptsev, F. T. Materiia kak filosofskaia kategoriia. Moscow, 1961.
Dialektika v naukakh o nezhivoi prirode, part 2. Moscow, 1964.
Filosofskie problemy fiziki elementarnykh chastits. Moscow, 1963.
Meliukhin, S. T. Materiia ve ee dinstve, beskonechnosti i razvitii. Moscow, 1966.
Meliukhin, S. T. Material’noe edinstvo mira v svete sovremennoi nauki. Moscow, 1967.
Struktura i for my materii. Moscow, 1967.
Kedrov, B. M. Lenin i revoliutsiia v estestvoznanii XX veka. Moscow, 1969.
Issledovaniia po obshchei teorii sistem. Moscow, 1969.
Lenin i sovremennoe estestvoznanie. Moscow, 1969.
Gott, V. S. Filosofskie voprosy sovremennoi fiziki. Moscow, 1972.



The substance composing bodies perceptible to the senses; includes any entity possessing mass when at rest.


1. Philosophy (in the writings of Aristotle and the Scholastics) that which is itself formless but can receive form and become substance
2. Philosophy (in the Cartesian tradition) one of two basic modes of existence, the other being mind: matter being extended in space as well as time
3. a secretion or discharge, such as pus
4. Law
a. something to be proved
b. statements or allegations to be considered by a court
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