heyday vs peak

heyday and peak both are nouns.

Word	Noun	Adjective	Verb	Adverb
heyday	Yes	No	No	No
peak	Yes	No	Yes	No

As nouns, heyday and peak are synonyms defined as:

Other synonyms of heyday include bloom, blossom, efflorescence, flower, flush, prime.

heyday (noun)	peak (noun)
the period of greatest prosperity or productivity	a brim that projects to the front to shade the eyes
	the top or extreme point of something (usually a mountain or hill)
	the highest point (of something)
	the most extreme possible amount or value
	a V shape
	the highest level or degree attainable; the highest stage of development
	the period of greatest prosperity or productivity

heyday (verb)	peak (verb)
	to reach the highest point; attain maximum intensity, activity