Authoritative

The word authority is derived from the Latin word auctoritas, meaning invention, advice, opinion, influence, or command. In English, the word authority can be used to mean power given by the state (in the form of Members of Parliament, Judges, Police Officers, etc.) or by academic knowledge of an area (someone can be an authority on a subject). The word Authority with capital A refers to the governing body upon which such authority (with lower case a) is vested; for example, the Puerto Rico Electric Power Authority or the Massachusetts Bay Transportation Authority.