obligation

noun

1. something by which a person is bound or obliged to do certain things, and which arises out of a sense of duty or results from custom, law, etc.
2. something that is done or is to be done for such reasons: to fulfill one’s obligations.
3. a binding promise, contract, sense of duty, etc.
4. the act of binding or obliging oneself by a promise, contract, etc.
5. Law.
   1. an agreement enforceable by law, originally applied to promises under seal.
   2. a document containing such an agreement.
   3. a bond containing a penalty, with a condition annexed for payment of money, performance of covenants, etc.
6. any bond, note, bill, certificate, or the like, as of a government or a corporation, serving as evidence of indebtedness.
7. an indebtedness or amount of indebtedness.
8. a favor, service, or benefit for which gratitude is due.
9. a debt of gratitude: He felt an obligation to his teacher.
10. the state of being under a debt, as of gratitude, for a favor, service, or benefit.

noun

1. a moral or legal requirement; duty
2. the act of obligating or the state of being obligated
3. law a legally enforceable agreement to perform some act, esp to pay money, for the benefit of another party
4. law
   1. a written contract containing a penalty
   2. an instrument acknowledging indebtedness to secure the repayment of money borrowed
5. a person or thing to which one is bound morally or legally
6. something owed in return for a service or favour
7. a service or favour for which one is indebted

n.c.1300, from Old French obligacion “obligation, duty, responsibility” (early 13c.) and directly from Latin obligationem (nominative obligatio) “an engaging or pledging,” literally “a binding” (but rarely used in this sense), noun of action from past participle stem of obligare (see oblige). The notion is of binding with promises or by law or duty.