Found:

Functional Projection

**SYNTAX: **The syntactic Xbar projection of a functional head,
such as COMP (**CP**), INFL (**IP**), or Det (**DP**). The underlying assumption is that, like lexical heads N, A, V and P, functional heads have a syntactic projection as dictated by **X-bar theory**. A fundamental question is whether there is a limit to the number of functional categories. It seems reasonable to assume that their
projection is in some sense parasitic on, or an extension of, a lexical projection.

LIT. | Abney, S. (1987) Chomsky, N. (1986b) Ouhalla, J. (1990) |