particle

noun

• 1a minute portion of matter:tiny particles of dust
• (also subatomic or elementary particle) Physics any of numerous subatomic constituents of the physical world that interact with each other, including electrons, neutrinos, photons, and alpha particles.
• Mathematics a hypothetical object having mass but no physical size.

• 2 [with negative] the least possible amount:he agrees without hearing the least particle of evidence

• 3 Grammar (in English) any of the class of words such as in, up, off, over, used with verbs to make phrasal verbs.
• (in ancient Greek) any of a class of words used for contrast and emphasis, such as de and ge.