grain - a small hard particle; "a grain of sand"

material, stuff - the tangible substance that goes into the makeup of a physical object; "coal is a hard black material"; "wheat is the stuff they use to make bread"

chylomicron - a microscopic particle of triglycerides produced in the intestines during digestion; in the bloodstream they release their fatty acids into the blood

flyspeck - a tiny dark speck made by the excrement of a fly

virion - (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

body - an individual 3-dimensional object that has mass and that is distinguishable from other objects; "heavenly body"

boson - any particle that obeys Bose-Einstein statistics but not the Pauli exclusion principle; all nuclei with an even mass number are bosons

deuteron - the nucleus of deuterium; consists of one proton and one neutron; used as a bombarding particle in accelerators

elementary particle, fundamental particle, subatomic particle - a particle that is less complex than an atom; regarded as constituents of all matter

fermion - any particle that obeys Fermi-Dirac statistics and is subject to the Pauli exclusion principle

ion - 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

micelle - an electrically charged particle built up from polymeric molecules or ions and occurring in certain colloidal electrolytic solutions like soaps and detergents

prion - (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

virino - (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

scintilla - a sparkling glittering particles

superstring - a hypothetical particle that is the elementary particle in a theory of space-time

thermion - an electrically charged particle (electron or ion) emitted by a substance at a high temperature

closed-class word, function word - a word that is uninflected and serves a grammatical function but has little identifiable meaning