Elvish was the language of the Elves.

Although of one origin (the language spoken by the Quendi at Cuiviénen, represented most closely by Quenya), Elvish split into a number of different dialects and languages, of which the only three named are Quenya, Sindarin and Silvan.

Elvish influenced the languages of the Edain a number of times, especially in Beleriand, when many Edain spoke Sindarin as their birth tongue. It also lent some influence in the Dúnedain kingdoms, where Westron was enriched with many Elvish words.
Encyclopedia entry originally written by tarkena