Languages typically construct phrases with a head (or nucleus) and zero or more dependents (modifiers). For example, in English a noun phrase can be constructed as follows:

• noun (e. g. "People")
• article + noun (e. g. "The man")
• article + adjective + noun (e. g. "The beautiful trees")
• article genitive noun + noun (e. g. "The woman's eyes")

etc.

In a noun phrase, the head is the main noun, and the dependents are the article, the adjective, and the genitive (-'s) noun.

There are also verb phrases, prepositional phrases, etc. In every case, the constituents are placed in a given order, which is more or less fixed according to the language in question. Also in some cases, the dependents can in turn be the heads of inner phrases (cf "the black cat's paws", "an awfully messy room", etc.).

Such ordering and nesting of phrases can be represented as a tree where branches can be divided into other minor branches, which may also branch in turn. This branching is typically ordered. In English, an article can only be added to a bare noun by placing it before the noun. An adjective can be added to an article-noun phrase only between the article and the noun (with a few exceptions). The direct object of a sentence is usually found after the verb, while the subject comes before the verb.

The rules exemplified above constitute the branching tendency of the language, which can be predominantly left-branching or right-branching.

Right-branching languages, such as Spanish and French, tend to place dependents after heads. Adjectives follow nouns, direct objects follow verbs, and adpositions are prepositional.

Left-branching languages, such as Japanese, tend to place heads after dependents. Adjectives precede nouns, direct objects come before verbs, and there are postpositions.

For most languages, the main branching tendency is just a tendency and it often shows exceptions. English, for example, shows left branching at the level of noun phrases, but is mostly right-branching at the sentence level. Spanish, which is overwhelmingly right-branching, allows adjectives before nouns and verbs before objects in many cases. Japanese, on the other hand, is practically a model for rigidly left-branching languages.