Structural grammar is a way of approaching the study of grammar, especially syntax, by analyzing the relationships among words in a sentence. Since the concept was first introduced in the early-to-mid-1900s, it has had a variety of applications in the classroom as well as in linguistic research. By the end of the 20th century, it had largely been combined with or absorbed into transformational grammar in primary and secondary education, but it remains a useful tool in linguistics — the scientific study of language.
Any time students are taught to recognize phrases, clauses, or even parts of speech, or to diagram sentences, they are learning structural grammar. It is no longer typically used in the US as the primary method of teaching grammar, however, and sentence diagramming has particularly fallen out of favor. By the late 20th and early 21st centuries, most classrooms in the US combined the structuralist approach with transformational grammar, in which students are asked to modify the structure of a sentence. For example, a student might be given the sentence "Mary had a little lamb," and be asked to transform it into a yes-or-no question: "Does Mary have a little lamb?" Additionally, this time period saw an increase in teaching structural aspects of grammar in relationship to composition, rather than as a separate study.
Despite decreasing use in pedagogy, structural grammar has long been an important approach in the specialized discipline of linguistics, although its applications have changed over the years. In contrast to previous methods of grammar teaching and research, especially prescriptive grammar, it focuses on vulnerable statements, which can be proven or unproven using the scientific method. As such, it was important in establishing linguistics as a truly scientific discipline.
In the middle of the 20th century, this approach to grammar was often applied to what was known as contrastive analysis, which is the comparison of the grammatical structures of two different languages. The intention was to use this research in the area of second language acquisition. Researchers hypothesized that speakers of one language would have particular difficulty learning a new language in areas where the two languages' structures are exceptionally different. This proved to be far less true than expected, however, so contrastive analysis was largely abandoned.
In the early 21st century, structural grammar is often assumed in linguistic research as part of other projects. Any area of linguistic research that involves syntax is likely to draw on work done by structural linguists. For instance, a linguist researching sentence processing might apply structuralist principles to various sentences as a step toward understanding how individuals come to understand them.