Editing Parse tree (section)

==Constituency-based parse trees==
The constituency-based parse trees of constituency grammars ([[phrase structure grammar]]s) distinguish between terminal and non-terminal nodes. The [[interior node]]s are labeled by [[nonterminal|non-terminal]] categories of the grammar, while the [[leaf node]]s are labeled by [[terminal symbol|terminal]] categories. The image below represents a constituency-based parse tree; it shows the syntactic structure of the [[English language|English]] sentence ''John hit the ball'':

[[File:Parse tree 1.jpg|Parse tree PSG]]

The parse tree is the entire structure, starting from S and ending in each of the leaf nodes (''John'', ''hit'', ''the'', ''ball''). The following abbreviations are used in the tree:

::* S for [[sentence (linguistics)|sentence]], the top-level structure in this example.

::* NP for [[noun phrase]]. The first (leftmost) NP, a single noun ''John'', serves as the [[subject (grammar)|subject]] of the sentence. The second one is the [[object (grammar)|object]] of the sentence.

::* VP for [[verb phrase]], which serves as the [[predicate (grammar)|predicate]].

::* V for [[verb]]; in this case, it's the [[transitive verb]] ''hit''.

::* D for [[determiner (class)|determiner]]; in this instance the [[article (grammar)|definite article]] ''the''.

::* N for [[noun]]; in this case ''ball''.

Each node in the tree is either a <em>root</em> node, a <em>branch</em> node, or a <em>leaf</em> node.<ref>See Carnie (2013:118ff.) for an introduction to the basic concepts of syntax trees (e.g. root node, terminal node, non-terminal node, etc.).</ref> A root node is a node that does not have any branches on top of it. Within a sentence, there is only ever one root node. A branch node is a parent node that connects to two or more child nodes. A leaf node, however, is a terminal node that does not dominate other nodes in the tree. S is the root node, NP and VP are branch nodes, and ''John'' (N), ''hit'' (V), ''the'' (D), and ''ball'' (N) are all leaf nodes. The leaves are the [[Lexical analysis|lexical tokens]] of the sentence. A parent node is one that has at least one other node linked by a branch under it. In the example, S is a parent of both N and VP. A child node is one that has at least one node directly above it to which it is linked by a branch of a tree. From the example, ''hit'' is a child node of V. The terms ''mother'' and ''daughter'' are also sometimes used for this relationship.