Syntactic Theory

Talking about Trees

Syntactic (and morphological) structure is usually depicted with a tree diagram. Like this one:

Basic structural notions in trees were already explained in the basic module on Syntax. See here!

When talking about trees, the following notions play a role.

• Basic notions:
  • node: a node is a position in a tree.
    The example tree has twelve nodes.
  • label: a label is a symbol that is written at the node.
    In the example, the labels are either syntactic categories (N, NP, V, Det, VP, S) or words (Pat, likes, my, cat).
  • dominance: A node A dominates a node B if A is higher in the diagram than B.
    A node A dominates a tree T if A dominates the highest node in T.
  • immediate dominance: a node A immediately dominates a node B if A is higher in the tree than B and there is exactly one line connecting A and B (i.e. there is no node C such that A, B, and C are distinct nodes and A dominates C and C dominates B).
  • local tree: A local tree is a tree that consists of a node A and exactly the nodes that are immediately dominated by the node A.
    The example tree has eight local trees. These are:
    

      
        S   NP    VP      NP     N    V     Det  N
       / \   |   /  \    /  \    |    |      |   |
      NP VP, N, V   NP, Det  N, Pat, likes, my, cat
    

• Tree metaphor:
  • root: The highest node in a tree is the root, i.e. the node that dominates all other nodes.
    In the example: the root is the node with label S.
  • leaf: A node at the bottom of the tree is a leaf, i.e. a node that does not dominate any other node.
    In the example: the nodes with labels Pat, likes, my and cat are the leaves.
  • branch: A branch of a node A is a sub-tree that is connected
    In the example, the root node (S) has two branches. The node Det has only one branch.
    • a binary branching node: A node that has two branches.
      In the example: the nodes with labels S and VP are binary branching. Also the rightmost node with label NP is binary branching.
    • ternary branching node: A node that has three branches.
      There is no such node in our example.
    • non-branching node (= unary branching node): A node that has one branch.
• Family metaphor:
  The following terms relate to local trees such as
  

       VP
      /  \
     V   NP
  

  • mother: A node A is the mother of a node B if A immediately dominates B.
    In the example, the node with label VP is the mother of the nodes labeled V and NP.
  • daughter: A node A is a daughter of a node B if B immediately dominates A.
    The example local tree has two daughters: the nodes with labels V and NP are the daughters of the node with label VP.
  • sister(s): node A is a sister of node B if they are leaves in the same local tree.
    In the example, the nodes with labels V and NP are sisters.
• Others:
  • yield: The yield of a tree is the series of words that are dominated by the root of the tree in the given order.
  • precedence: A node A precedes a node B in a tree with root C if the yield of the tree dominated by A precedes the yield of the tree dominated by B in the yield of the tree dominated by C.
    In the example, the node V precedes the second NP node, because its yield (likes) precedes the yield of the NP (my cat). However, the V node does not precede the VP node, because the yield of the tree dominated by the V node is part of the yield of the tree dominated by the VP node.

Categories: Glossary