Original sentence: A descriptive grammar attempts to describe actual usage, avoiding prescriptive judgements.A descriptive grammar of a speech community where "I didn't do nothing" is acceptable will treat that sentence as grammatical, and provide rules that account for it.A prescriptive grammar presents authoritative norms for a particular language, and tends to deprecate non-standard constructions.For example, in many dialects of English, the use of double negatives is very common, though ungrammatical from the point of view of a prescriptive English grammar.Though prescriptive grammars remain common in pedagogy and foreign language teaching, they have fallen out of favor in modern academic linguistics, as they describe only a subset of actual language usage
Edited sentence: A descriptive grammar is a grammar that describes the language as it is actually used by people, regardless of whether prescriptive grammars would consider a construction correct or not.A descriptive grammar of a speech community where people acceptably say "I didn't do nothing" will treat that sentence as grammatical, and provide rules that account for it.A prescriptive grammar is a grammar that asserts itself as the only correct formulation of a particular language, and rejects any other constructions as wrong.For example, in many dialects of English, the use of double negatives is very common, even though prescriptive English grammars explicitly reject double negatives as ungrammatical.Though prescriptive grammars remain quite common in pedagogy and foreign language teaching, they have fallen out of favor in modern academic linguistics, as they represent only a limited subset of how people actually use a language