What is "subjacency"

Subjacency is a general syntactic locality constraint on movement. It specifies restrictions placed on movement and regards it as a strictly local process. This term was first defined by Noam Chomsky in 1973 and constitutes the main concept of the Government and Binding Theory. The revised definition of subjacency from Chomsky (1977) is as follows: "A cyclic rule cannot move a phrase from position Y to position X (or conversely) in … X … [α… [β… Y … ] … ] … X …, where α and β are cyclic nodes. Cyclic nodes are S and NP", (where S= Sentence and NP= Noun Phrase).

This principle states that no movement can move an element over more than one bounding node at a time. In more recent frameworks, bounding nodes which are hurdles to movement are AgrP ( Agreement Phrase) and DP ( Determiner Phrase) (S and NP in Chomsky’s definition respectively). Therefore, Subjacency condition limits movement by defining bounding nodes. It also accounts for the fact that all movements are local.