the state of being held captive

physical detention by force

something a person must do because of morality, law, conscience etc

responsibility, assignment

something that it is essential to see, do, hear etc; (used to express an obligation or an order)

necessity, essential

a condition, fact, of feeling that something necessary is absent; things considered to be necessary; misfortune, bad circumstance

want, requirement

a promise, duty or condition that shows what action ought to be taken (e.g. the law, one's duty, a sense of what is right)

responsibility

(used to tell a person about a present or past duty or obligation) (used to express an opinion, give advice etc about the present or past)

necessity, essential