The T-unit is the shortest amount of writing that sentences can be split into, according to grammatical rules. Experts define the T-unit as a main clause with possible subordinate clauses attached. This term was invented by someone named Kellogg Hunt in the 1960s. Language analysts use it to learn more about how people use a given language, and how to preserve grammatical correctness in speech and writing.
Linguists and other academics can debate whether the T-unit is inherently a sentence, or whether it’s best to call this unit of speech a phrase. Generally, T-units have most of the characteristics of a complete sentence. To look at some of the briefer examples of T-units, it’s helpful to know that all that is needed for a complete sentence is a subject noun and a verb. For example, a simple two word phrase like “I ran” can be classified as either a T-unit or a complete sentence; other more colorful examples include those referenced by famous writer Stephen King, such as “plums deify.” Although these small bits of language can help a beginner to understand T-units, longer sentences will give them opportunities to break down a more complex phrase into individual free-standing parts.
Larger analysis of the T-unit can often benefit from an understanding of how longer sentences can be broken down into multiple T-units. A linguistics instructor, or a professor in some other academic areas, might ask students to break down a sentence like this into T-units: “I walked west and I came to a house.” Here, technically speaking, the sentence could be broken down into two separate T-units: “I walked west. I came to a house.” If, however, the original sentence was “I walked west until I came to a house,” the two units cannot be separated without sacrificing some meaning. This is just one case where knowing the rules for T-units will come in handy in grammatical analysis of speech or text.
Linguists also often talk about the various kinds of clauses that are attached to a T-unit. These clauses are often the reasons why the sentence cannot be split into smaller parts. Some of these kinds of clauses include adverbial clauses and other subordinate clauses that are largely descriptive, and include prepositions. Learning about the different kinds of subordinate clauses can help make a student very good at identifying and parsing T-units.