tack on vs attach

tack on and attach both are verbs.

Word	Noun	Adjective	Verb	Adverb
tack on	No	No	Yes	No
attach	No	No	Yes	No

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

tack on (verb)	attach (verb)
fix to; attach	become attached
	cause to be attached
	be attached; be in contact with
	take temporary possession of as a security, by legal authority
	create social or emotional ties