(law) An indefeasible right or title, distinguished from a contingent interest, which could be defeated (i.e. cease) if a certain event occurred.

(banking, finance) Interest, as on a loan or a bank account, that is calculated on the total on the principal plus accumulated unpaid interest.

(finance) The total number of contracts outstanding between market participants in a market for futures, options, or other derivatives.

An advocacy group.

Having self-interest; particularly concerned for oneself.

(law enforcement, chiefly Canada, US) Someone who police have reason to believe may have a connection to a crime, or to possess important information relating to that crime, but who has not been accused or charged by authorities nor been officially deemed to be a suspect.

(law) A right, typically in the form of regular income, that lasts for the lifetime of the person benefiting from that right.

(idiomatic) a desire for, or interest in, the success of a particular person or group, often a sports team

(law, US, idiomatic) the reason of case dismissal used when the judge decides that justice will be best served when the case is dismissed

plural of interest group