Descriptive grammar refers to a system by which language is studied that attempts to understand how words and ideas are assembled in language, rather than assigning rules to how language should be constructed. This type of grammar is typically based on observation and research into a language and its various dialects. From this research, grammarians are able to discern how people actually use language and then establish rules or systems for language construction based on that usage. Descriptive grammar is in contrast to prescriptive grammar, in which rules are created based on how a grammarian believes language should be properly constructed.
In linguistics and grammatical research, there are typically two approaches to language study and grammar: prescriptive and descriptive. These different approaches allow grammarians to consider different aspects of language construction and determine different rules regarding a language based on those approaches. Descriptive grammar is typically used by those interested in how language is actually used, rather than how language should be used or what may be considered “proper” language. Researchers and descriptive grammarians often interview people or find samples of recorded language from a natural context to observe and understand how people use language.
Since descriptive grammar is based on actual usage, it can still be used to create rules related to a particular language, but these are based on how people speak. In English, for example, there is a descriptive rule that an article typically precedes a noun in a noun phrase, such as “the dog” or “a hat.” This rule is not based on a sense of how English language should be used, but instead based on observations of English speakers using the language. Descriptive grammar is about understanding language in natural use, and creating rules or guidelines to better codify and comprehend linguistic structures.
In contrast to descriptive grammar, prescriptive grammar is an approach designed around understanding how language should be constructed. Many of the rules that language learners are taught in a classroom, especially young students learning language, are based on a prescriptive understanding of language. While both prescriptive and descriptive grammar are equally important and simply approach the study of language in different ways, there can be issues with a purely prescriptive approach. The commonly cited rule forbidding a preposition at the end of a sentence, for example, is a prescriptive rule based on the grammatical rules of Latin. Many grammarians have argued against this rule for more than a century, and insist that ending a sentence in a preposition is perfectly acceptable in English.