2.1.5  Structural terminology

Now that we have introduced the notion of structure, we need some terms to use to refer to aspects of structures and the way we can represent them. The notion of structure entails that there are elements of a sentence that themselves are made up of other elements and indeed that these other elements may be made up of yet more elements, and so on and so on. The elements that make up a larger part of the structure are called its constituents and the constituents that directly make up a part of structure are called its immediate constituents. Thus, in a phrase such as the following, the verb and its complement phrase are its immediate constituents. Everything inside the complement phrase is a constituent of the whole phrase, though not an immediate constituent:

(28)

This kind of representation of grammatical structure is called a tree diagram, though unlike real trees, grammatical trees tend to grow downwards. The elements that make up the tree, the words and phrases etc. are called nodes and the lines that join the nodes are branches.

Finally, it is often useful to talk about two or more nodes in a tree and their relationships to each other. For this purpose a syntactic tree is seen like a family tree with the nodes representing different family members. For some reason however, these families are made up of women only. A node which has immediate constituents is called the mother of those constituents and the constituents are its daughters. Two nodes which have the same mother are sisters.

So to refer to the tree in (28) again, the top P node is the mother of the verb and the P node which represents the verb’s complement. The verb and the complement P node are therefore sisters. The complement P node is also a mother to the pronoun his and the noun decision and again these two nodes are sisters.

It would of course be possible to define the relationships ‘grandmother’, ‘aunt’, ‘cousin’ etc. for any given tree diagram. However these relationships tend not to be very important for syntactic processes and so we will not consider them.

There is another popular way of representing structure, which we have made some use of above without comment. This is the use of brackets to represent constituents. For example, the sentence we discussed above the postwoman pestered the doctor on his birthday can be represented as follows:

(29)

[[the postwoman] [pestered [the doctor] [on [his birthday]]]]

The way this works is that each constituent is surrounded by square brackets and so a constituent can be determined by finding an open bracket ‘[’ to its left and the corresponding close bracket ‘]’ to the right. Thus, the postwoman in (29) is defined as a constituent as it has an open bracket immediately to its left and a close bracket immediately to its right.

Admittedly, it is harder to see the structure of a sentence when represented with brackets than with a tree, as it takes some working out which open brackets go along with which close bracket. However, bracketings are a lot more convenient to use, especially if we only want to concentrate on certain aspects of a structure. So, for example, above we represented an embedded sentence using brackets:

(30)

Kate claimed [Geoff jeopardised the expedition]

This partial bracketing demonstrates at a glance how the main sentence contains an embedded one and so bracketing can be a very useful way of describing simple structures.

The bracketing in (29) is not entirely equivalent to the tree diagram in (16) as in the tree the nodes have labels that tell us what they represent, phrases or sentences. We can add labels to brackets to make the two representations equivalent. With bracketing, the label is usually placed on the open bracket of the constituent:

(31)

[S [P the postwoman] [P pestered [P the doctor] [P on [P his birthday]]]]

Again, this adds to the complexity of the representation and so it is not as clear as the tree diagram. But providing it is not too complex, it is still a useful way to represent structural details.