Branching (linguistics)

In linguistics, branching refers to the shape of the parse trees that represent the structure of sentences. Assuming that the language is being written or transcribed from left to right, parse trees that grow down and to the right are right-branching, and parse trees that grow down and to the left are left-branching. The direction of branching reflects the position of heads in phrases, and in this regard, right-branching structures are head-initial, whereas left-branching structures are head-final. English has both right-branching (head-initial) and left-branching (head-final) structures, although it is more right-branching than left-branching. Some languages such as Japanese and Turkish are almost fully left-branching (head-final). Some languages are mostly right-branching (head-initial), for example, Arabic.

Languages typically construct phrases with a head word (or nucleus) and zero or more dependents (modifiers). The following phrases show the phrase heads in bold.

Examples of left-branching phrases (= head-final phrases):

Examples of right-branching phrases (= head-initial phrases):

Examples of phrases that contain both left- and right-branching (= head-medial phrases):

Concerning phrases such as the house and the house there, this article assumes the traditional NP analysis, meaning that the noun is deemed to be head over the determiner. On a DP-analsyis (determiner phrase), the phrase the house would be right-branching instead of left-branching.

Left- and right-branching structures are illustrated with the trees that follow. Each example appears twice, once according to a constituency-based analysis associated with a phrase structure grammar and once according to a dependency-based analysis associated with a dependency grammar. The first group of trees illustrate left-branching:

The upper row shows the constituency-based structures, and the lower row the dependency-based structures. In the constituency-based structures, left-branching is present (but not really visible) in so far as the non-head daughter is to the left of the head. In the corresponding dependency-based structures in the lower row, the left-branching is clear; the dependent appears to the left of its head, the branch extending down to the left. The following structures demonstrate right-branching:

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