stiffen vs restrict

stiffen and restrict both are verbs.

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

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

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

stiffen (verb)	restrict (verb)
become stiff or stiffer	place limits on (extent or amount or access)
make stiff or stiffer	place restrictions on
severely restrict in scope or extent	place under restrictions; limit access to by law
	prevent (information) from being circulated or disclosed