noun (n)

• (nontechnical usage) a tiny piece of anything(noun.substance)

  Synonym:
  atom, corpuscle, molecule, mote, speck
  

  source: wordnet30
• a body having finite mass and internal structure but negligible dimensions(noun.object)

  Synonym:
  subatomic particle
  

  source: wordnet30
• a function word that can be used in English to form phrasal verbs(noun.communication)

  source: wordnet30
• 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.(noun)

  source: webster1913