What is a synonym for obligation?

Here are some synonyms for obligation, depending on the context:

Formal:

* Duty

* Responsibility

* Liability

* Commitment

* Mandate

* Requirement

* Burden

Informal:

* Debt

* Promise

* Pledge

* Need

* Must

Other options:

* Moral obligation: This emphasizes the ethical aspect of the obligation.

* Legal obligation: This emphasizes the binding nature of the obligation under the law.

* Financial obligation: This refers to a monetary obligation.

The best synonym to use will depend on the specific situation and the nuance you want to convey.