'obligation' definitions:

Definition of 'obligation'

From: WordNet
noun
The social force that binds you to the courses of action demanded by that force; "we must instill a sense of duty in our children"; "every right implies a responsibility; every opportunity, an obligation; every possession, a duty"- John D.Rockefeller Jr [syn: duty, responsibility, obligation]
noun
The state of being obligated to do or pay something; "he is under an obligation to finish the job"
noun
A personal relation in which one is indebted for a service or favor [syn: obligation, indebtedness]
noun
A written promise to repay a debt [syn: debt instrument, obligation, certificate of indebtedness]
noun
A legal agreement specifying a payment or action and the penalty for failure to comply

Synonyms of 'obligation'

From: Moby Thesaurus