liability vs obligation

liability and obligation both are nouns.

Word	Noun	Adjective	Verb	Adverb
liability	Yes	No	No	No
obligation	Yes	No	No	No

As nouns, obligation is a hypernym of liability; that is, obligation is a word with a broader meaning than liability:

liability (noun)	obligation (noun)
the quality of being something that holds you back	the social force that binds you to the courses of action demanded by that force
an obligation to pay money to another party	a legal agreement specifying a payment or action and the penalty for failure to comply
the state of being legally obliged and responsible	a written promise to repay a debt
	a personal relation in which one is indebted for a service or favor
	the state of being obligated to do or pay something