ETYM Latin particula, dim of pars, gen partis, a part: cf. French particule. Related to Part, Parcel.
1. A body having finite mass and internal structure but negligible dimensions.
2. A function word having different uses in different languages.
A subatomic object with a definite mass and charge.
In grammar, a category that includes such words as up, down, in, out, which may be used either as prepositions (also called prepositional particles), as in up the street and down the stairs, or as adverbs (identified as adverbial particles), as in pick up the book/pick the book up. A verb with a particle (for example, put up) is a phrasal verb.