Nonpolar
Part of speech: adjective
Definition: not containing a dipole not ionic; not dissociating into ions when dissolved in water etc
Particle
Part of speech: noun
Definition: A body with very small size; a fragment.An elementary particle or subatomic particle.A word that has a particular grammatical function but does not obviously belong to any particular part of speech, such as the word to in English infinitives or O as the vocative particle.
Example sentence: I had been interested in particle physics, which deals with the fundamental constituents of matter.