constantly vs forever

constantly and forever both are adverbs.

Word	Noun	Adjective	Verb	Adverb
constantly	No	No	No	Yes
forever	No	No	No	Yes

As adverbs, constantly and forever are synonyms defined as:

Other synonyms of constantly include always, incessantly, perpetually.

constantly (adverb)	forever (adverb)
invariably	for a limitless time
without variation or change, in every case	for a very long or seemingly endless time
	invariably