stiffen vs limit

stiffen is not a noun while limit is a noun.

Word	Noun	Adjective	Verb	Adverb
stiffen	No	No	Yes	No
limit	Yes	No	Yes	No

As verbs, limit is a hypernym of stiffen; that is, limit is a word with a broader meaning than stiffen:

Other hypernyms of stiffen include bound, confine, restrict, throttle, trammel.

stiffen (noun)	limit (noun)
	the greatest possible degree of something
	the boundary of a specific area
	as far as something can go
	the greatest amount of something that is possible or allowed
	the mathematical value toward which a function goes as the independent variable approaches infinity
	final or latest limiting point

stiffen (verb)	limit (verb)
become stiff or stiffer	restrict or confine within limits
make stiff or stiffer	place limits on (extent or amount or access)
severely restrict in scope or extent	decide upon or fix definitely