Obligation (noun)

1. The action of obliging or the state of being obliged to do something.
2. A binding promise or undertaking.

Origin:

Middle english, from latin obligatio, from obligare to bind, oblige.

Examples:

1. I have an obligation to my family.
2. He felt a sense of obligation to help.
3. The company had an obligation to its employees.
4. The contract set out the obligations of both parties.
5. It is my moral obligation to speak out.