weaken vs loosen

weaken and loosen both are verbs.

Word	Noun	Adjective	Verb	Adverb
weaken	No	No	Yes	No
loosen	No	No	Yes	No

As verbs, loosen is a hyponym of weaken; that is, loosen is a word with a more specific, narrower meaning than weaken:

weaken (verb)	loosen (verb)
become weaker	become loose or looser or less tight
lessen the strength of	make loose or looser
reduce the level or intensity or size or scope of	make less dense
lessen in force or effect	disentangle and raise the fibers of
destroy property or hinder normal operations	cause to become loose
	become less severe or strict
	make less severe or strict