touch on vs modify

touch on and modify both are verbs.

Word	Noun	Adjective	Verb	Adverb
touch on	No	No	Yes	No
modify	No	No	Yes	No

As verbs, modify is a hypernym of touch on; that is, modify is a word with a broader meaning than touch on:

Other hypernyms of touch on include alter, change.

touch on (verb)	modify (verb)
restore by replacing a part or putting together what is torn or broken	make less severe or harsh or extreme
have an effect upon	add a modifier to a constituent
refer to or discuss briefly	cause to change; make different; cause a transformation
be relevant to