Definition of "particle"

particle

/ˈpɑːtɪk(ə)l/

noun
plural particles
1. A very small piece of matter, a fragment; especially, the smallest possible part of something.
2. (physics) Any of various physical objects making up the constituent parts of an atom; an elementary particle or subatomic particle.
  Quotations
  What, he asked himself, does quantum theory have to say about the familiar properties of particles such as position?
  2011, Brian Cox, Jeff Forshaw, The Quantum Universe, Allen Lane, published 2011, page 55
  The physics of elementary particles in the 20th century was distinguished by the observation of particles whose existence had been predicted by theorists sometimes decades earlier.
  2012 March-April, Jeremy Bernstein, “A Palette of Particles”, in American Scientist‎, volume 100, number 2, page 146
3. (linguistics) A part of speech that has no inherent lexical definition but must be associated with another word to impart meaning, often a grammatical category: for example, the English word to in a full infinitive phrase (to eat) or O in a vocative phrase (O Canada), or as a discourse marker (mmm).
  Quotations
  In English there is no grammatical device to differentiate predicational judgments from nonpredicational descriptions. This distinction does cast a shadow on the grammatical sphere to some extent, but recognition of it must generally be made in semantic terms. It is maintained here that in Japanese, on the other hand, the distinction is grammatically realized through the use of the two particles wa and ga.
  1965 June 4, Shigeyuki Kuroda, “Generative grammatical studies in the Japanese language”, in DSpace@MIT‎, retrieved 2014-02-24, page 38
  Traditional grammar typically recognises a number of further categories: for example, in his Reference Book of Terms in Traditional Grammar for Language Students, Simpson (1982) posits two additional word-level categories which he refers to as Particle, and Conjunction. Particles include the italicised words {...}(a) He put his hat on(b) If you pull too hard, the handle will come off(c) He was leaning too far over the side, and fell out(d) He went up to see the manager
  1988, Andrew Radford, Transformational grammar: a first course, Cambridge, UK: Cambridge University Press, page 133
4. (linguistics) A part of speech which cannot be inflected.
  Quotations
  322. The parts of speech which are neither declined nor conjugated, are called by the general name of particles. 323. They are adverbs, prepositions, conjunctions, and interjections.
  1844, E. A. Andrews: First Lessions in Latin; or Introduction to Andrews and Stoddard's Latin Grammar. (6th edition, Boston), p.91 (at books.google)
  The Parts of Speech are the Noun (Substantive and Adjective), the Pronoun, the Verb, and the Particles (Adverb, Preposition, and Conjunction)[.]
  1894 (2008), B. L. Gildersleeve & G. Lodge: Gildersleeve's Latin Grammar (reprint of the 3rd edition by Dover, 2008), p.9. (at books.google)
5. (Christianity) In the Roman Catholic church, a crumb of consecrated bread; also the smaller breads used in the communion of the laity.
6. A little bit.
  Quotations
  "That doesn't make a particle of difference", replied Charlotte. "Not a particle."
  1952, E.B. White, Charlotte's Web, page 89