Editing Phrase (section)

==Phrase trees==
Many theories of syntax and grammar illustrate sentence structure using phrase '[[parse tree|trees]]', which provide schematics of how the words in a sentence are grouped and relate to each other. A tree shows the words, phrases, and clauses that make up a sentence. Any word combination that corresponds to a complete subtree can be seen as a phrase.

There are two competing principles for constructing trees; they produce 'constituency' and 'dependency' trees and both are illustrated here using an example sentence. The constituency-based tree is on the left and the dependency-based tree is on the right (where [[adjective]] (A), [[Determiner (linguistics)|determiner]] (D), [[noun]] (N), sentence (S), [[verb]] (V), [[noun phrase]] (NP), [[prepositional phrase]] (PP), [[verb phrase]] (VP)):

::[[File:The_house_at_the_end_of_the_street.jpg|alt=|Trees illustrating phrases]]

The tree on the left is of the constituency-based, [[phrase structure grammar]], and the tree on the right is of the [[dependency grammar]]. The node labels in the two trees mark the [[syntactic category]] of the different [[constituent (linguistics)|constituents]], or word elements, of the sentence.

In the constituency tree each phrase is marked by a phrasal node (NP, PP, VP); and there are eight phrases identified by phrase structure analysis in the example sentence. On the other hand, the dependency tree identifies a phrase by any node that exerts dependency upon, or dominates, another node. And, using dependency analysis, there are six phrases in the sentence.

The trees and phrase-counts demonstrate that different theories of syntax differ in the word combinations they qualify as a phrase. Here the constituency tree identifies three phrases that the dependency trees does not, namely: ''house at the end of the street'', ''end of the street'', and ''the end''. More analysis, including about the plausibilities of both grammars, can be made empirically by applying [[constituent (linguistics)|constituency tests]].