[Indefinite]

Это зависит от строгости определения языка и диалекта. Толкин называл его и так, и так:
"although the dialects of the Silvan Elves, when they again met their long separated kindred, had so far diverged from Sindarin as to be hardly intelligible, little study was needed to reveal their kinship as Eldarin tongues" (UT). WJ confirms that the Sindar recognized the Green-elves "as kinsfolk of Lindarin origin (...), using a tongue that in spite of great differences was still perceived to be akin to their own" (Ardalambion).

Обычно называют языком, тем более, что к Третьей эпохе он уже был мертвым.