Ossiriandeb (Os.), also: Ossiriandic, Ossiriandrin, Ossiriandish, Laiquenderin or simply Green-Elvish, was a distinct Elvish tongue spoken by the Laiquendi (Green-Elves) of Ossiriand, the land of the Seven Rivers in Beleriand. It was a dialect of Nandorin (but closely related to Sindarin), a branch of the Telerin language, which itself derived from Common Eldarin. Ossiriandeb was among the most unique and least-documented Elven languages of the First Age, evolving in relative isolation and diverging from its ancestral tongues as the Green-Elves settled in the forests and riverlands of Ossiriand.
The language was known for its melodic, flowing nature, deeply inspired by the rhythm of water, the whisper of leaves, and the song of the wind. Unlike the Quenya of the High Elves, Ossiriandeb retained many archaisms of Telerin and at the same time was highly influenced by naturalistic and lyrical elements of Sindarin.