In semantics, a modifier is said to be restrictive (or defining) if it restricts the reference of its head. For example, in "the red car is fancier than the blue one", red and blue are restrictive, because they restrict which cars car and one are referring to. ("The car is fancier than the one" would make little sense.) By contrast, in "John's beautiful wife", beautiful is non-restrictive; presuming John has only one wife, "John's wife" identifies her sufficiently, while "beautiful" only serves to add more information. (Note that in the case, unusual in the West, that John had multiple wives, only one of whom was considered "beautiful", the modifier could be used in the restrictive sense.)
Restrictive modifiers are also called defining, identifying, essential, or necessary; non-restrictive ones are also called non-defining, non-identifying, descriptive, or unnecessary (though this last term can be misleading). In certain cases, generally when restrictiveness is marked syntactically through the lack of commas, restrictive modifiers are called integrated and non-restrictive ones are called non-integrated or supplementary.
Contents |
English does not generally mark modifiers for restrictiveness. The only modifiers that are consistently marked for restrictiveness are relative clauses: non-restrictive ones are set off in writing by using commas, and in speech through intonation (with a pause beforehand and an uninterrupted melody), while restrictive ones are not. Further, while restrictive clauses are often headed by the relative pronoun that or by a zero relative pronoun, non-restrictive clauses are not. For example:
(*In formal American English, the use of which as a restrictive pronoun is often considered to be incorrect. See That or which.)
While English does not consistently mark ordinary adjectives for restrictiveness, they can be marked by moving them into relative clauses. For example, "the red car is fancier than the blue one" can be rewritten as, "the car that's red is fancier than the one that's blue," and "John's beautiful wife" can be rewritten as "John's wife, who is beautiful." English speakers do not generally find such locutions necessary, however.
Spanish and Portuguese are notable for marking all descriptive adjectives for restrictiveness: restrictive adjectives follow their nouns, while non-restrictive (explicative) ones precede them. Italian employs the same mechanism to an extent. An example in Portuguese:
Many languages, such as German and Japanese, do not mark restrictiveness explicitly. In Dutch, only written language distinguishes restrictive clauses by leaving out the comma that would normally follow the noun.
French tends to mark restrictive clauses in the same way as English, and the Hebrew Academy endorses English-style punctuation (though it is not in universal use among Hebrew-speakers).
Turkish has a tendency to assume restrictiveness in adjectives more so than in English, in some cases requiring that non-restrictiveness be specified. For example, if the English sentence "He came with his tall son" were translated mechanically "Uzun boylu oğluyla geldi", it would be understood to mean both that the man in question has more than one son, and that he came with the tallest of them, neither of which is understood from the English sentence. Even the rendering "Uzun boylu olan oğluyla geldi", "He came with his son who is tall", would be understood similarly. Neither can commas be used to specify restrictiveness or non-restrictiveness. A translator would have to provide the information that the son is tall separately, eg. "Uzun boylu bir oğlu vardı; onunla birlikte geldi" ("He had a tall son; he came with him").
On the intonation question, see Beverly Colins and Inger M. Mees, Practical Phonetics and Phonology, Routledge 2003.