Deletion

Deletion is the erasing of (at least) the phonological features of an element in a representation. In early versions of generative grammar, deletion was constrained by the principle of recoverability of deletion. In current work, recoverability is partly captured by the ECP. Deletion counts as a possible instantiation of affect alpha.

Example
complementizer deletion (I know [that] he comes) may be an instance of deletion subject to the ECP.

Link
Utrecht Lexicon of Linguistics