adjournment vs postponement

adjournment and postponement both are nouns.

Word	Noun	Adjective	Verb	Adverb
adjournment	Yes	No	No	No
postponement	Yes	No	No	No

As nouns, postponement is a hypernym of adjournment; that is, postponement is a word with a broader meaning than adjournment:

Other hypernyms of adjournment include deferment, deferral.

adjournment (noun)	postponement (noun)
the termination of a meeting	act of putting off to a future time
the act of postponing to another time or place	time during which some action is awaited