node, so that the entire phrase is identified as a noun phrase (NP). In the dependency trees on the right, the noun projects only a single node, whereby this node dominates the one node that the adjective projects, a situation that also identifies the entirety as an NP. The constituency trees are structurally the same as their dependency counterparts, the only difference being that a different convention is used for marking heads and dependents. The conventions illustrated with these trees are just a couple of the various tools that grammarians employ to identify heads and dependents. While other conventions abound, they are usually similar to the ones illustrated here. More trees The four trees above show a head-final structure. The following trees illustrate head-final structures further as well as head-initial and head-medial structures. The constituency trees (= a-trees) appear on the left, and dependency trees (= b-trees) on the right. Henceforth the convention is employed where the words appear as the labels on the nodes. The next four trees are additional examples of head-final phrases: The following six trees illustrate head-initial phrases: And the following six trees are examples of head-medial phrases: The head-medial constituency trees here assume a more traditional n-ary branching analysis. Since some prominent phrase structure grammars (e.g. most work in Government and binding theory and the Minimalist Program) take all branching to be binary, these head-medial a-trees may be controversial. X-bar trees Trees that are based on the X-bar schema also acknowledge head-initial, head-final, and head-medial phrases, although the depiction of heads is less direct. The standard X-bar schema for English is as follows: This structure is both head-initial and head-final, which makes it head-medial in a sense. It is head-initial insofar as the head X0 precedes its complement, but it is head-final insofar as the projection X' of the head follows its specifier. Head-initial vs. head-final languages Some language typologists classify language syntax according to a head directionality parameter in word order, that is, whether a phrase is head-initial (= right-branching) or head-final (= left-branching), assuming that it has a fixed word order at all. English is more head-initial than head-final, as illustrated with the following dependency tree of the first sentence of Franz Kafka's The Metamorphosis: The tree shows the extent to which English is primarily a head-initial language. Structure is descending as speech and processing move from left to right. Most dependencies have