darken vs alter

darken and alter both are verbs.

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

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

Other hypernyms of darken include change, modify.

darken (verb)	alter (verb)
become dark or darker	remove the ovaries of
make dark or darker	become different in some particular way, without permanently losing one's or its former characteristics or essence
tarnish or stain	cause to change; make different; cause a transformation
	insert words into texts, often falsifying it thereby
	make an alteration to