A word used to join phrases, clauses or words. Conjunctions may be coordinating or subordinating.
Example: and, but, your, neither, nor, either, or (coordinating); when, while, as, before, until, after, since, if, unless, as, than, like, though.(subordinating)
Words which show the relationship between nouns.
Example: at, on, by, opposite, under, in, on, from, for, through, towards.
Words which substitute for nouns or noun phrases.
Example: I, you, her, he, she, it, we, them, they, theirs, me, us, ours, yours, myself.