The Turkic language Sakha (Yakut) uses a copular verb with predicate nominals but not with predicate adjectives or verbs in certain environments, including relative clauses, nominalized clauses, and complements to nouns. Previous work takes this as evidence that adjectives but not nouns are true one-place predicates. However, unaccusativity diagnostics show that adjectives pattern with nouns in Sakha, as in other languages: neither is inherently predicative without a predicative functional head. The need for a copula with predicate nominais in certain environments can be explained using Richards’s distinctiveness condition. Relative clauses, noun complements, and nominalization structures all bring a nominal head in close contact with the predicate. If the predicate itself is nominal, a verbal copula must intervene to separate the predicate from the embedding head of the same category.
