名詞 past.:

1. the time that has elapsed
   同義詞：past, past times, yesteryear, yore
2. a earlier period in someone's life (especially one that they have reason to keep secret)
   同義詞：past
3. a verb tense that expresses actions or states in the past
   同義詞：past, past tense

形容詞 past.:

1. earlier than the present time; no longer current
   同義詞：past
2. of a person who has held and relinquished a position or office
   同義詞：past, preceding, retiring
3. a verb tense or other construction referring to events or states that existed at some previous time
   同義詞：past

副詞 past.:

1. so as to pass a given point
   同義詞：by, past