Traditionally, a dependency grammar belongs to the class of grammars that emphasize words rather than constituents.
Grammars that are built primarily on constituents are known as phrase structure grammars. Phrase structure grammars are thus constituent-based,
while dependency grammars are word-based.
While phrase structure grammars see sentences and clauses structured in terms of constituents, dependency grammars assume that sentence and clause structure derives from dependency relationships between words. The difference is illustrated in the trees below:
Tree (or phrase marker) (a) shows what a traditional phrase structure grammar would view as the structure of the sentence They killed
the man with a gun. One can see, for instance, that the preposition with forms a prepositional phrase with the noun phrase
a gun. Compare this to the dependency tree (b): here the preposition dominates the noun gun, which in turn
dominates the article a.
When one compares the number of nodes across the two trees, one finds that (a) contains 12 nodes, while (b) only contains 7 nodes. On the assumption that two representations convey the same utterance, the one that does so without explanatory deficiencies is called more minimal with respect to the other. In general, dependency grammars are more minimal than phrase structure grammars because they assume less structure.
A second point to acknowledge is that the term grammar can have two meanings; one meaning is rather general and refers to how linguistic units are structured.
In this broader sense, grammar is a hyperonym to syntax, morphology, and phonology. The narrow meaning refers only to syntax.
The word grammar in dependency grammar is traditionally understood in the narrow sense, i.e. dependency grammars are theories of syntax, but not theories of
morphology or phonology. The motivation for understanding dependency grammars as dependency syntaxes comes from their being word-based. Historically, dependency
grammars have struggled to establish themselves in the broader sense of grammar.
The grammar explained here differs from traditional dependency grammars insofar as it is catena-based. Since catenae operate in syntax as well as in morphology, a catena-based dependency grammar can hope to become a grammar in the broader sense. Even though the ultimate aim is to see the distinction between syntax and morphology as a continuum, the discussion here will branch out into a syntax section and a morphology section.