strengthen vs alter

strengthen and alter both are verbs.

Word	Noun	Adjective	Verb	Adverb
strengthen	No	No	Yes	No
alter	No	No	Yes	No

As verbs, alter is a hypernym of strengthen; that is, alter is a word with a broader meaning than strengthen:

Other hypernyms of strengthen include change, modify.

strengthen (verb)	alter (verb)
give a healthy elasticity to	remove the ovaries of
gain strength	become different in some particular way, without permanently losing one's or its former characteristics or essence
make strong or stronger	cause to change; make different; cause a transformation
	insert words into texts, often falsifying it thereby
	make an alteration to