In theoretical linguistics, a distinction is made between endocentric and exocentric constructions. A grammatical construction (e.g. a phrase or compound word) is said to be endocentric if it fulfills the same linguistic function as one of its parts, and exocentric if it does not. The distinction reaches back at least to Bloomfield's work of the 1930s. Such a distinction is possible only in phrase structure grammars (constituency grammars), since in dependency grammars all constructions are necessarily endocentric.