There was the common tongue, Westron, derivated from the old númenorean language, that was spoken by almost every people in the known world. However, most peoples (even those who spoke Westron) had their own language: the Elves, the Dwarves, the Rohirrim (whose language is very alike the Westron - Tolkien used Old-English to represent this relation, as English represents the Westron -; the Haradrim, Easterlings and Orcs had several tongues (as they were divided in many tribes).