Summary

Every phrase contains a head and possibly, but not necessarily, one or more modifiers. Each clause has a head, the verb. There are two types of modifiers, namely complements and adjuncts. Adjuncts are optional; complements are typically obligatory and are always mentioned in the lexical entries for verbs (or nouns or prepositions). Many collocation restrictions apply to heads and complements (but also to phrases other than complements). Heads and complements are typically adjacent; where a head has two or more complements, adjuncts typically come before or after the sequence of head and complements.