Editing Parse tree (section)

==Nomenclature==
[[Image:parseTree.svg|right|150px|thumb|A simple parse tree]]
A parse tree is made up of nodes and branches.<ref>{{Cite web|url=https://www1.essex.ac.uk/linguistics/external/clmt/latex4ling/trees/parsetree/|title=The parsetree Package for Drawing Trees in LaTeX|publisher=University of Essex}}</ref> In the picture the parse tree is the entire structure, starting from S and ending in each of the leaf nodes (John, ball, the, hit). In a parse tree, each node is either a ''root'' node, a ''branch'' node, or a ''leaf'' node. In the above example, S is a root node, NP and VP are branch nodes, while John, ball, the, and hit are all leaf nodes.

Nodes can also be referred to as parent nodes and child nodes. A ''parent'' node is one which has at least one other node linked by a branch under it. In the example, S is a parent of both NP and VP. A ''child'' node is one which has at least one node directly above it to which it is linked by a branch of the tree. Again from our example, hit is a child node of V.

A '''nonterminal function''' is a function (node) which is either a root or a branch in that tree whereas a '''terminal function''' is a function (node) in a parse tree which is a leaf.

For binary trees (where each parent node has two immediate child nodes), the number of 
possible parse trees for a sentence with ''n'' words is given by the [[Catalan number]] <math>C_n</math>.