noun

• The act of binding oneself by a social, legal, or moral tie to someone.
• A social, legal, or moral requirement, duty, contract, or promise that compels someone to follow or avoid a particular course of action.
• A course of action imposed by society, law, or conscience by which someone is bound or restricted.
• (law) A legal agreement stipulating a specified action or forbearance by a party to the agreement; the document containing such agreement.
• (countable) Reason for being obliged to, that is, grateful for, something.