Many theories of syntax and grammar illustrate sentence structure using phrase 'trees', which provide schematics of how the words in a sentence are grouped and relate to each other. Trees show the words, phrases, and, at times, clauses that make up sentences.[2] Any word combination that corresponds to a complete subtree can be seen as a phrase.
There are two established and 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: