T-unit


In linguistics, the term T-unit was coined by Kellogg Hunt in 1965. It is defined as the "shortest grammatically allowable sentences into which or minimally terminable unit." Often, but not always, a T-unit is a sentence.
More technically, a T-unit is a dominant clause and its dependent clauses: as Hunt said, it is "one main clause with all subordinate clauses attached to it". T-units are often used in the analysis of written and spoken discourse, such as in studies on errors in second language writing. The number of error-free T-units may be counted, as in Robb et al., or changes in accuracy per T-unit over drafts of compositions may be measured.
Young gives some examples of what a T-unit is and is not:

"The following elements were counted as one T-unit: a single clause, a matrix plus subordinate clause, two or more phrases in apposition, and fragments of clauses produced by ellipsis. Co-ordinate clauses were counted as two t-units. Elements not counted as t-units include backchannel cues such as mhm and yeah, and discourse boundary markers such as okay, thanks or good. False starts were integrated into the following t-unit."