Page "Disputes in English grammar" Paragraph 33

The prescriptivist and descriptivist approaches often clash: the former prescribes how English should be spoken — a teacher showing students how to write ; the latter describes how English is spoken — a sociolinguist studying word use in a population.

An extreme prescriptivist might maintain that even if every sentence in current English uses a certain construction, that construction may still be incorrect.

Conversely, an extreme descriptivist might maintain that there is no such thing as incorrect use.

In practice, however, speakers lie between these two extremes, holding that because English changes with time and is governed in large measure by convention, a construction may be considered correct once it is used by a majority of speakers, but also that a given sentence is incorrect if it violates the conventions of English that apply to its context.