|Abstract:||We examine different cases of ineffability, not only in phonology and syntax, but also in morphology and semantics, and propose a typology of ineffabilities compatible with the Control component of Orgun & Sprouse (1999). Lexical gaps as well as other gaps in the morpho-syntax or the phonology are the primary source of ineffable ? or absolutely ungrammatical ? constructions. Further gaps arise from the need to reconcile incompatible features. Whether such instances are repaired is language dependent. Islands and other restrictions resulting from syntactic and semantic laws on scope and wh-words form the third group of ineffable cases. The upshot of our study is that neither the lexicon-based nor the semantic ineffability cases are a problem for Optimality Theory, since they are located in domains of grammar for which OT?s architecture cannot be held responsible.