weaken vs undermine

weaken and undermine both are verbs.

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

As verbs, weaken and undermine are synonyms defined as:

Other synonyms of weaken include counteract, countermine, sabotage, subvert.

weaken (verb)	undermine (verb)
become weaker	hollow out as if making a cave or opening
lessen the strength of	destroy property or hinder normal operations
reduce the level or intensity or size or scope of
lessen in force or effect
destroy property or hinder normal operations