back up vs substantiate

back up and substantiate both are verbs.

Word	Noun	Adjective	Verb	Adverb
back up	No	No	Yes	No
substantiate	No	No	Yes	No

As verbs, substantiate is a hypernym of back up; that is, substantiate is a word with a broader meaning than back up:

Other hypernyms of back up include affirm, confirm, corroborate, support, sustain.

back up (verb)	substantiate (verb)
establish as valid or genuine	solidify, firm, or strengthen
become or cause to become obstructed	establish or strengthen as with new evidence or facts
make a copy of (a computer file) especially for storage in another place as a security copy	make real or concrete; give reality or substance to
move backwards from a certain position	represent in bodily form
give moral or psychological support, aid, or courage to