(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
Cases of word usage
1) money that is owing and that ought to have been paid (arrears)
2) the consciousness within oneself of the choice one ought to make between right and wrong (conscience)
3) 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) (obligation)
