perpetual vs constant

perpetual is not a noun while constant is a noun.

Word	Noun	Adjective	Verb	Adverb
perpetual	No	Yes	No	No
constant	Yes	Yes	No	No

As adjectives, perpetual and constant are synonyms defined as:

perpetual and constant: uninterrupted in time and indefinitely long continuing

Other synonyms of perpetual include ceaseless, incessant, never-ending, unceasing, unremitting.

perpetual (noun)	constant (noun)
	a quantity that does not vary
	a number representing a quantity assumed to have a fixed value in a specified mathematical context

perpetual (adjective)	constant (adjective)
uninterrupted in time and indefinitely long continuing	steadfast in purpose or devotion or affection
continuing forever or indefinitely	uninterrupted in time and indefinitely long continuing
	unvarying in nature