mend vs touch on

mend is a noun but touch on is not a noun.

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

As verbs, mend and touch on are synonyms defined as:

mend and touch on: restore by replacing a part or putting together what is torn or broken

Other synonyms of mend include bushel, doctor, fix, furbish up, repair, restore.

mend (noun)	touch on (noun)
the act of putting something in working order again
sewing that repairs a worn or torn hole (especially in a garment)

mend (verb)	touch on (verb)
restore by replacing a part or putting together what is torn or broken	restore by replacing a part or putting together what is torn or broken
heal or recover	have an effect upon
	refer to or discuss briefly
	be relevant to