Prescriptive linguistics is the study of how language should be used based on established norms and rules, rather than only describing how language is actually used. It aims to establish standards for areas like spelling, grammar, pronunciation and syntax. Advocates of prescriptive linguistics, like Samuel Johnson and Robert Lowth, believe standardized languages aid communication and wish to provide guidelines for effective writing. The subfields of prescriptive linguistics include semantics, syntax, grammar, corpus linguistics, hypercorrection, language policy, language purism, and pleonasm.