Parse Tree - Constituency-based Parse Trees

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:

This parse tree is simplified; for more information, see X-bar theory. 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. S is the root node, NP and VP are branch nodes, and John, hit, the, and ball are all leaf nodes. The leaves are the lexical tokens of the sentence. 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 NP 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 the tree. From the example, hit is a child node of V. The terms mother and daughter are also sometimes used for this relationship.