weaken vs slow down

weaken and slow down both are verbs.

Word	Noun	Adjective	Verb	Adverb
weaken	No	No	Yes	No
slow down	No	No	Yes	No

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

weaken (verb)	slow down (verb)
become weaker	become less tense, rest, or take one's ease
lessen the strength of	lose velocity; move more slowly
reduce the level or intensity or size or scope of	become slow or slower
lessen in force or effect	reduce the speed of
destroy property or hinder normal operations	cause to proceed more slowly