Linguistic prescription, or prescriptive grammar, is the attempt to establish rules defining preferred or correct usage of language. These rules may address such linguistic aspects as spelling, pronunciation, vocabulary, syntax, and semantics. Sometimes informed by linguistic purism, such normative practices may suggest that some usages are incorrect, inconsistent, illogical, lack communicative effect, or are of low aesthetic value. They may also include judgments on socially proper and politically correct language use.