approximate vs cypher

approximate is not a noun while cypher is a noun.

Word	Noun	Adjective	Verb	Adverb
approximate	No	Yes	Yes	No
cypher	Yes	No	Yes	No

As verbs, cypher is a hypernym of approximate; that is, cypher is a word with a broader meaning than approximate:

Other hypernyms of approximate include calculate, cipher, compute, figure, reckon, work out.

approximate (noun)	cypher (noun)
	a secret method of writing
	a message written in a secret code
	a person of no influence
	a quantity of no importance; thing (object:), singular, negative pronoun; pronoun, thing, singular; quantifier: negative existential
	a mathematical element that when added to another number yields the same number

approximate (verb)	cypher (verb)
judge tentatively or form an estimate of (quantities or time)	make a mathematical calculation or computation
be close or similar	convert ordinary language into code