time lag vs postponement

time lag and postponement both are nouns.

Word	Noun	Adjective	Verb	Adverb
time lag	Yes	No	No	No
postponement	Yes	No	No	No

As nouns, time lag and postponement are synonyms defined as:

Other synonyms of time lag include delay, hold, wait.

time lag (noun)	postponement (noun)
time during which some action is awaited	act of putting off to a future time
	time during which some action is awaited