noun (n)

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

  Synonym:
  atom, molecule, mote, particle, speck
  

  source: wordnet30
• either of two types of cells (erythrocytes and leukocytes) and sometimes including platelets(noun.body)

  Synonym:
  blood cell, blood corpuscle
  

  source: wordnet30
• A minute particle; an atom; a molecule.(noun)

  source: webster1913
• An electron.(noun)

  source: webster1913