Nouns

(n)past, past times, yesteryearthe time that has elapsed“forget the past”
(n)pasta earlier period in someone's life (especially one that they have reason to keep secret)“reporters dug into the candidate's past”
(n)past, past tensea verb tense that expresses actions or states in the past

Adjectives

(a)pastearlier than the present time; no longer current“time past”, “his youth is past”, “this past Thursday”, “the past year”
(s)past, preceding, retiringof a person who has held and relinquished a position or office“a retiring member of the board”

Adverbs

(r)by, pastso as to pass a given point“every hour a train goes past”