A particle is a small piece of anything. Particle can also refer to a subatomic particle with mass and structure, but takes up hardly any space at all.

Particles are tiny. If you mean a subatomic particle, that's a body that you can't see because it is so incredibly small, though it does have a miniscule mass and internal structure. These particles are even smaller than atoms. You can also say a crumb or speck of something is a particle. Dust particles are piling up all the time, and vacuuming cleans up lots of particles. Those particles are little bits of things. In both cases, particles are very tiny.

Definitions of particle
  1. noun
    (nontechnical usage) a tiny piece of anything
    synonyms: atom, corpuscle, molecule, mote, speck
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    a relatively small granular particle of a substance
    material resulting from the process of grinding
    a microscopic particle of triglycerides produced in the intestines during digestion; in the bloodstream they release their fatty acids into the blood
    a tiny dark speck made by the excrement of a fly
    identification particle
    a tiny particle of material that can be added to a product to indicate the source of manufacture
    a tiny grain
    (trademark) a microscopic and traceable identification particle used to trace explosives or other hazardous materials or to prevent counterfeiting
    type of:
    material, stuff
    the tangible substance that goes into the makeup of a physical object
  2. noun
    a body having finite mass and internal structure but negligible dimensions
    synonyms: subatomic particle
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    (virology) a complete viral particle; nucleic acid and capsid (and a lipid envelope in some viruses)
    alpha particle
    a positively charged particle that is the nucleus of the helium atom; emitted from natural or radioactive isotopes
    beta particle
    a high-speed electron or positron emitted in the decay of a radioactive isotope
    any particle that obeys Bose-Einstein statistics but not the Pauli exclusion principle; all nuclei with an even mass number are bosons
    the nucleus of deuterium; consists of one proton and one neutron; used as a bombarding particle in accelerators
    elementary particle, fundamental particle
    (physics) a particle that is less complex than an atom; regarded as constituents of all matter
    any particle that obeys Fermi-Dirac statistics and is subject to the Pauli exclusion principle
    a particle that is electrically charged (positive or negative); an atom or molecule or group that has lost or gained one or more electrons
    magnetic monopole
    a hypothetical particle with a single magnetic pole instead of the usual two
    an electrically charged particle built up from polymeric molecules or ions and occurring in certain colloidal electrolytic solutions like soaps and detergents
    (microbiology) an infectious protein particle similar to a virus but lacking nucleic acid; thought to be the agent responsible for scrapie and other degenerative diseases of the nervous system
    (microbiology) a hypothetical infectious particle thought to be the cause of scrapie and other degenerative diseases of the central nervous system; consists of nucleic acid in a protective coat of host cell proteins
    a sparkling glittering particle
    a hypothetical particle that is the elementary particle in a theory of space-time
    an electrically charged particle (electron or ion) emitted by a substance at a high temperature
    a negatively charged ion
    the antiparticle of a lepton
    a particle that has the same mass as another particle but has opposite values for its other properties; interaction of a particle and its antiparticle results in annihilation and the production of radiant energy
    the antiparticle of a quark
    baryon, heavy particle
    any of the elementary particles having a mass equal to or greater than that of a proton and that participate in strong interactions; a hadron with a baryon number of +1
    a positively charged ion
    gauge boson
    a particle that mediates the interaction of two elementary particles
    any elementary particle that interacts strongly with other particles
    an elementary particle that participates in weak interactions; has a baryon number of 0
    meson, mesotron
    an elementary particle responsible for the forces in the atomic nucleus; a hadron with a baryon number of 0
    (physics) hypothetical truly fundamental particle in mesons and baryons; there are supposed to be six flavors of quarks (and their antiquarks), which come in pairs; each has an electric charge of +2/3 or -1/3
    strange particle
    an elementary particle with non-zero strangeness
    cosmic string, string
    (cosmology) a hypothetical one-dimensional subatomic particle having a concentration of energy and the dynamic properties of a flexible loop
    WIMP, weakly interacting massive particle
    a hypothetical subatomic particle of large mass that interacts weakly with ordinary matter through gravitation; postulated as a constituent of the dark matter of the universe
    type of:
    an individual 3-dimensional object that has mass and that is distinguishable from other objects
  3. noun
    a function word that can be used in English to form phrasal verbs
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    type of:
    closed-class word, function word
    a word that is uninflected and serves a grammatical function but has little identifiable meaning
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