An element that looks like the definite article (German d-, English th-) is found not only in immediately pre-nominal position (the food) but also, e.g., in clause-initial position (th-at John is ill), in pre-adjectival position (the blue fish), inside definite demonstratives (th-is), and inside of certain quantifiers (bo-th). I will discuss reasons to think that these occurrences have commonalities that go beyond their looks and which are relevant to determining their syntactic status. Concretely, I will argue that th- in the blue fish, th-is, and bo-th, is a head in the adjective phrase, and that its relation to the adjective is comparable to that of the complementizer to the verb of its clause. This recalls the analysis of adnominal adjectives as reduced relatives. Pursuing this line, and recognizing the adjectival nature of determiners/quantifiers, I arrive at the conclusion that German jeder ‘every’ has a complex internal syntax, akin to that of a reduced relative.
At a more abstract level, d-/th- spells out a left peripheral head independently of the nature of the lexical category (V, N, or A) that “heads” the relevant extended projection. Merger of this head alternates (within and across languages) with (phrasal) movement of the “lexical head” of the projection (verb, noun, or adjective) to the left periphery.