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A parse tree or parsing tree〔See Chiswell and Hodges 2007: 34.〕 or derivation tree or (concrete) syntax tree is an ordered, rooted tree that represents the syntactic structure of a string according to some context-free grammar. The term ''parse tree'' itself is used primarily in computational linguistics; in theoretical syntax the term ''syntax tree'' is more common. Parse trees are distinct from the abstract syntax trees used in computer programming, in that their structure and elements more concretely reflect the syntax of the input language. They are also distinct from (although based on similar principles to) the sentence diagrams (such as Reed-Kellogg diagrams) sometimes used for grammar teaching in schools. Parse trees are usually constructed based on either the constituency relation of constituency grammars (phrase structure grammars) or the dependency relation of dependency grammars. Parse trees may be generated for sentences in natural languages (see natural language processing), as well as during processing of computer languages, such as programming languages. A related concept is that of phrase marker or P-marker, as used in transformational generative grammar. A phrase marker is a linguistic expression marked as to its phrase structure. This may be presented in the form of a tree, or as a bracketed expression. Phrase markers are generated by applying phrase structure rules, and themselves are subject to further transformational rules. ==Constituency-based parse trees== The constituency-based parse trees of constituency grammars (= phrase structure grammars) distinguish between terminal and non-terminal nodes. The interior nodes are labeled by non-terminal categories of the grammar, while the leaf nodes are labeled by terminal categories. The image below represents a constituency-based parse tree; it shows the syntactic structure of the English sentence ''John hit the ball'': :::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, the top-level structure in this example :: * NP for noun phrase. The first (leftmost) NP, a single noun "John", serves as the subject of the sentence. The second one is the object of the sentence. :: * VP for verb phrase, which serves as the predicate :: * V for verb. In this case, it's a transitive verb ''hit''. :: * D for determiner, in this instance the definite article "the" :: * N for noun Each node in the tree is either a ''root'' node, a ''branch'' node, or a ''leaf'' node.〔See Carnie (2013:118ff.) for an introduction to the basic concepts of syntax trees (e.g. root node, terminal node, non-terminal node, etc.).〕 A root node is a node that doesn't have any branches on top of it. Within a sentence, there is only ever one root node. A branch node is a mother node that connects to two or more daughter 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 tokens of the sentence.〔See Alfred et al. 2007.〕 A node can also be referred to as ''parent'' node or a ''child'' node. 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. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Parse tree」の詳細全文を読む スポンサード リンク
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