Dependency Syntax and Universal Dependencies

Changing dog bites man to man bites dog changes the subject and object even though the words stay the same. Part-of-speech tags identify word categories, and morphological features describe properties such as number and tense. Neither layer by itself records which noun is the subject of bites. A dependency analysis makes that grammatical relationship explicit.

Syntax is the level of linguistic representation that connects word-level information to sentence-level meaning. A tagger can tell you that a token is a verb, and a morphological analyzer can tell you that it is past tense and third-person singular, but neither tells you that the verb is the main predicate of the clause, that a particular noun is its subject, or that another noun is its direct object. Those relational facts identify grammatical roles and attachments. They can support an interpretation of who acted or what was given to whom, but a syntactic subject is not always an agent, and syntax alone does not recover the full event meaning. This chapter is about a representation that makes the grammatical relations explicit.

In the previous chapter we met one representation of syntax: constituency trees. Words group into phrases (NP, VP, S), and phrases nest inside larger phrases. Context-free grammars describe this kind of phrase structure. But it is not the only option. This chapter is about a competing representation, dependency syntax, in which every word is a node and every grammatical relation is a directed edge from a head to a dependent.

The dependency view asks which word is the head of each other word. In She gave him a book., the verb gave has four direct dependents: She (nsubj), him (iobj), book (obj), and the period (punct). The determiner a depends on book. Reordering the words can leave these grammatical relations unchanged, though information structure and annotation conventions still matter. Dependency representation separates attachment from linear position without assuming that every reordering preserves the same analysis.

Dependency trees are the backbone of Universal Dependencies (UD), a community project for cross-linguistically consistent morphological and syntactic annotation. Its common inventories and CoNLL-U format support comparisons across treebanks, while language-specific guidelines and extensions preserve distinctions that a single universal label cannot settle. A shared label inventory helps make analyses comparable; it does not make different languages or annotation decisions identical. UD's introduction describes that balance.

The rest of the chapter builds up the representation from first principles. We define what a dependency tree is, what makes a word a head, what projectivity means, and how labels encode grammatical roles. Then we look at UD itself: its design choices, word-level annotations, and its data format. Finally we read a bounded CoNLL-U sample, check its basic-tree constraints, draw two of its trees, and test projectivity. These checks make the representation precise enough to use in a later parsing or extraction workflow.