burden of proof vs obligation

burden of proof and obligation both are nouns.

Word	Noun	Adjective	Verb	Adverb
burden of proof	Yes	No	No	No
obligation	Yes	No	No	No

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

burden of proof: the duty of proving a disputed charge
obligation: the social force that binds you to the courses of action demanded by that force

Other hypernyms of burden of proof include duty, responsibility.

burden of proof (noun)	obligation (noun)
the duty of proving a disputed charge	the social force that binds you to the courses of action demanded by that force
	a legal agreement specifying a payment or action and the penalty for failure to comply
	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