Feature checking

Feature checking is a Notion in checking theory. Feature checking is a relation between two elements such that one or more designated features they share are eliminated.

Example
in who did you see the +wh feature of who is checked in the specifier position of CP (spec,CP) against the +wh feature of C. If who or C do not check their +wh feature, the derivation crashes (cf. *you saw who).

Link
Utrecht Lexicon of Linguistics