carry back vs subtract

carry back and subtract both are verbs.

Word	Noun	Adjective	Verb	Adverb
carry back	No	No	Yes	No
subtract	No	No	Yes	No

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

carry back: deduct a loss or an unused credit from taxable income for a prior period
subtract: make a subtraction

Other hypernyms of carry back include deduct, take off.

carry back (verb)	subtract (verb)
deduct a loss or an unused credit from taxable income for a prior period	take off or away
	make a subtraction