commencement vs showtime

commencement and showtime both are nouns.

Word	Noun	Adjective	Verb	Adverb
commencement	Yes	No	No	No
showtime	Yes	No	No	No

As nouns, commencement and showtime are synonyms defined as:

commencement and showtime: the time at which something is supposed to begin

Other synonyms of commencement include beginning, first, get-go, kickoff, offset, outset, start, starting time.

commencement (noun)	showtime (noun)
the act of starting something	the time at which something is supposed to begin
an academic exercise in which diplomas are conferred
the time at which something is supposed to begin