*particle*

n. (Physics) A fundamental particle which has the same mass as one of the common fundamental particles, but which has an opposite charge, and for which certain other of the properties (e. g. baryon number, strangeness) may be opposite to that of the normal particle. The antiparticle to an electron is called a positron; the antiparticle to a proton is called an antiproton; the antiparticle to a neutron is called an antineutron. When a particle and its corresponding antiparticle collide, they typically annihilate each other with the production of large quantities of energy, usually in the form of radiation. The interaction of a proton and antiproton cause annihilation with production of mesons. [ PJC ]

n. [ L. particula, dim. of pars, gen partis, a part: cf. F. particule. See Part, and cf. Parcel. ] 1. A minute part or portion of matter; a morsel; a little bit; an atom; a jot; as, a particle of sand, of wood, of dust. [ 1913 Webster ]

The small size of atoms which unite
To make the smallest particle of light. Blackmore. [ 1913 Webster ]

2. Any very small portion or part; the smallest portion; as, he has not a particle of patriotism or virtue. [ 1913 Webster ]

The houses had not given their commissioners authority in the least particle to recede. Clarendon. [ 1913 Webster ]

3. (R. C. Ch.) (a) A crumb or little piece of consecrated host. (b) The smaller hosts distributed in the communion of the laity. Bp. Fitzpatrick. [ 1913 Webster ]

4. (Gram.) A subordinate word that is never inflected (a preposition, conjunction, interjection); or a word that can not be used except in compositions; as, ward in backward, ly in lovely. [ 1913 Webster ]

4. (Physics) An elementary particle. [ PJC ]

n. (Physics) A large and expensive scientific instrument used by physicists to accelerate elementary particles (such as protons or electrons) to speeds near that of light, for the purpose of investigating the fundamental properties of matter; sometimes also called an atom smasher, since the particles thus accelerated are often directed at targets of atoms which are fragmented by the impact into their more fundamental component particles. The particles generated by impact of a beam in an accelerator on its target are detected by various types of detecting apparatus, and procedures are required to sort and identify the many particles created. The fundamental particles generated by impacts in a particle accelerator are often those not actually present inside atoms; and in certain types of particle accelerator, such as the colliding beam accelerator, the impact which generates energetic particles is with other fundamental particles, and not with atoms. [ PJC ]