Linguistic prescription is the establishment of rules defining publicly preferred usage of language, including rules of spelling, pronunciation, vocabulary, grammar, etc. Linguistic prescriptivism may aim to establish a standard language, teach what a particular society or sector of a society perceives as a correct or proper form, or advise on effective and stylistically apt communication. If usage preferences are conservative, prescription might appear resistant to language change; if radical, it may produce neologisms. Such prescriptions may be motivated by consistency (making a language simpler or more logical); rhetorical effectiveness; tradition; aesthetics or personal preferences; linguistic purism or nationalism (i.e. removing foreign influences); or to avoid causing offense (etiquette or political correctness).

Prescriptive approaches to language are often contrasted with the descriptive approach of academic linguistics, which observes and records how language is actually used (while avoiding passing judgment). The basis of linguistic research is text (corpus) analysis and field study, both of which are descriptive activities. Description may also include researchers' observations of their own language usage. In the Eastern European linguistic tradition, the discipline dealing with standard language cultivation and prescription is known as "language culture" or "speech culture".

Despite being apparent opposites, prescriptive and descriptive approaches have a certain degree of conceptual overlap as comprehensive descriptive accounts must take into account and record existing speaker preferences, and a prior understanding of how language is actually used is necessary for prescription to be effective. Since the mid-20th century some dictionaries and style guides, which are prescriptive works by nature, have increasingly integrated descriptive material and approaches. Examples of guides updated to add more descriptive material include Webster's Third New International Dictionary (1961) and the third edition Garner's Modern English Usage (2009) in English, or the Nouveau Petit Robert (1993) in French. A partially descriptive approach can be especially useful when approaching topics of ongoing conflict between authorities, or in different dialects, disciplines, styles, or registers. Other guides, such as The Chicago Manual of Style, are designed to impose a single style and thus remain primarily prescriptive (as of 2017^[update]).

Some authors define "prescriptivism" as the concept where a certain language variety is promoted as linguistically superior to others, thus recognizing the standard language ideology as a constitutive element of prescriptivism or even identifying prescriptivism with this system of views. Others, however, use this term in relation to any attempts to recommend or mandate a particular way of language usage (in a specific context or register), without, however, implying that these practices must involve propagating the standard language ideology. According to another understanding, the prescriptive attitude is an approach to norm-formulating and codification that involves imposing arbitrary rulings upon a speech community, as opposed to more liberal approaches that draw heavily from descriptive surveys; in a wider sense, however, the latter also constitute a form of prescriptivism.

Mate Kapović makes a distinction between "prescription" and "prescriptivism", defining the former as "a process of codification of a certain variety of language for some sort of official use", and the latter as "an unscientific tendency to mystify linguistic prescription".

Linguistic prescription is a part of a language standardization process. The chief aim of linguistic prescription is to specify socially preferred language forms (either generally, as in Standard English, or in style and register) in a way that is easily taught and learned. Prescription may apply to most aspects of language, including spelling, pronunciation, vocabulary, morphology, syntax, and semantics.

Prescription is useful for facilitating inter-regional communication, allowing speakers of divergent dialects to understand a standardized idiom used in broadcasting, for example, more readily than each other's dialects. ^{[citation needed]} While such a lingua franca may evolve by itself, the tendency to formally codify and normalize it is widespread in most parts of the world.^{[citation needed]} Foreign language instruction is also considered a form of prescription, since it involves instructing learners how to speak, based on usage documentation laid down by others.

Linguistic prescription may also be used to advance a social or political ideology. Throughout history, prescription has been created around high-class language, and therefore it degeneralizes lower-class language. This has led to many justifications of classism, as the lower-class can easily be portrayed to be incoherent and improper if they do not speak the standard language. This also corresponds to the use of prescription for racism, as dialects spoken by what is seen as the superior race are usually standardized in countries with prominent racism. A good example of this is the demeaning of AAVE in the United States, as the idea that the "lower race" speaks improperly is propagated by people with an opposing ideology.