A relative clause is a subordinate clause that modifies a noun phrase, most commonly a noun. For example, the phrase “the man who wasn’t there” contains the noun man, which is modified by the relative clause who wasn’t there. A relative clause can also modify a pronoun, as in “he to whom I have written“, or a noun phrase which already contains a modifier, as in “the black panther in the tree, which is about to pounce“. The complete phrase (modified noun phrase plus modifying relative clause) is also a noun phrase.
In many European languages, relative clauses are introduced by a special class of pronouns called relative pronouns; in the previous example, who is a relative pronoun. In other languages, relative clauses may be marked in different ways: they may be introduced by a special class of conjunctions called relativizers; the main verb of the relative clause may appear in a special morphological variant; or a relative clause may be indicated by word order alone. In some languages, more than one of these mechanisms may be possible.
Types of relative clause
A relative clause is always used to join together two sentences that share one of their arguments. For example, the sentence “The man that I saw yesterday went home” is equivalent to the following two sentences: “The man went home. I saw the man yesterday.” In this case, “the man” occurs as argument to both sentences. Note that there is no requirement that the shared argument fulfills the same role in both of the joined sentences; indeed, in this example, “the man” is subject of the first, but direct object of the second.
The two sentences joined in a relative-clause construction are known as the main clause or matrix clause (the outer clause) and the embedded clause or relative clause (the inner clause). The shared noun as it occurs in the main clause is termed the head noun. Languages differ in many ways in how relative clauses are expressed:
- How the role of the shared noun phrase is indicated in the embedded clause.
- How the two clauses are joined together.
- Where the embedded clause is placed relative to the head noun (in the process indicating which noun phrase in the main clause is modified).
For example, the English sentence “The man that I saw yesterday went home” can be described as follows:
- The role of the shared noun in the embedded clause is indicated by gapping (i.e. in the embedded clause “that I saw yesterday”, a gap is left after “saw” to indicate where the shared noun would go).
- The clauses are joined by the complementizer “that”.
- The embedded clause is placed after the head noun “the man”.
The following sentences indicate various possibilities (only some of which are grammatical in English):
- “The man [that I saw yesterday] went home”. (A complementizer linking the two clauses with a gapping strategy indicating the role of the shared noun in the embedded clause. One possibility in English. Very common cross-linguistically.)
- “The man [I saw yesterday] went home”. (Gapping strategy, with no word joining the clauses—also known as a reduced relative clause. One possibility in English. Used in Arabic when the head noun is indefinite, as in “a man” instead of “the man”.)
- “The man [whom I saw yesterday] went home”. (A relative pronoun indicating the role of the shared noun in the embedded clause — in this case, the direct object. Used in formal English, as in Latin, German or Russian.)
- “The man [seen by me yesterday] went home”. (A reduced relative clause, in this case passivized. One possibility in English.)
- “The man [that I saw him yesterday] went home”. (A complementizer linking the two sentences with a resumptive pronoun indicating the role of the shared noun in the embedded clause, as in Arabic, Hebrew or Persian.)
- “The man [that him I saw yesterday] went home”. (Similar to the previous, but with the resumptive pronoun fronted. This occurs in modern Greek and as one possibility in modern Hebrew; the combination that him of complementizer and resumptive pronoun behaves similar to a unitary relative pronoun.)
- “The [I saw yesterday]’s man went home”. (Preceding relative clause with gapping and use of a possessive particle — as normally used in a genitive construction — to link the relative clause to the head noun. This occurs in Chinese and certain other languages influenced by it.)
- “The [I saw yesterday] man went home”. (Preceding relative clause with gapping and no linking word, as in Japanese.)
- “The man [of my seeing yesterday] went home”. (Nominalized relative clause, as in Turkish.)
- “[Which man I saw yesterday], that man went home”. (A correlative structure, as in Hindi.)
- “[I saw the man yesterday] went home.” (An unreduced, internally-headed relative clause, as in Tibetan or Navajo.)
Strategies for indicating the role of the shared noun in the relative clause
There are four main strategies for indicating the role of the shared noun phrase in the embedded clause. These are typically listed in order of the degree to which the noun in the relative clause has been reduced, from most to least:
- Gap strategy or gapped relative clause
- Relative pronoun
- Pronoun retention
Gapped relative clause
In this strategy, there is simply a gap in the relative clause where the shared noun would go. This is normal in English, for example, and also in Chinese and Japanese. This is the most common type of relative clause, especially in verb-final languages with prenominal relative clauses, but is also widespread among languages with postnominal externally headed relative clauses.
There may or may not be any marker used to join the relative and main clauses. (Note that languages with a case-marked relative pronoun are technically not considered to employ the gapping strategy even though they do in fact have a gap, since the case of the relative pronoun indicates the role of the shared noun.) Often the form of the verb is different from that in main clauses and is to some degree nominalized, as in Turkish and in English reduced relative clauses.
In non-verb-final languages, apart from languages like Thai and Vietnamese with very strong politeness distinctions in their grammars, gapped relative clauses tend however to be restricted to positions high up in the accessibility hierarchy. With obliques and genitives, non-verb-final languages that do not have politeness restrictions on pronoun use tend to use pronoun retention. English is unusual in that all roles in the embedded clause can be indicated by gapping: e.g. “I saw the man who is my friend”, but also (in progressively less accessible positions cross-linguistically, according to the accessibility hierarchy described below) “… who I know”, “… who I gave a book to”, “… who I spoke with”, “… who I run slower than”. Usually, languages with gapping disallow it beyond a certain level in the accessibility hierarchy, and switch to a different strategy at this point. Classical Arabic, for example, only allows gapping in the subject and sometimes the direct object; beyond that, a resumptive pronoun must be used. Some languages have no allowed strategies at all past a certain point — e.g. in many Austronesian languages, such as Tagalog, all relative clauses must have the shared noun serving the subject role in the embedded clause. In these languages, relative clauses with shared nouns serving “disallowed” roles can be expressed by passivizing the embedded sentence, thereby moving the noun in the embedded sentence into the subject position. This, for example, would transform “The man who I gave a book to” into “The man who was given a book by me”. Generally, languages such as this “conspire” to implement general relativization by allowing passivization from all positions – hence a sentence equivalent to “The man who is run slower than by me” is grammatical. Note also that gapping is often used in conjunction with case-marked relative pronouns (since the relative pronoun indicates the case role in the embedded clause), but this is not necessary (e.g. Chinese and Japanese both using gapping in conjunction with an indeclinable complementizer).
Relative pronoun type
This is in fact a type of gapped relative clause, but is distinguished by the fact that the role of the shared noun in the embedded clause is indicated indirectly by the case marking of the marker (the relative pronoun) used to join the main and embedded clauses. All languages which use relative pronouns have them in clause-initial position: though one could conceivably imagine a clause-final relative pronoun analogous to an adverbial subordinator in that position, they are unknown.
Note that some languages have what are described as “relative pronouns” (in that they agree with some properties of the head noun, such as number and gender) but which don’t actually indicate the case role of the shared noun in the embedded clause. Classical Arabic in fact has “relative pronouns” which are case-marked, but which agree in case with the head noun. Case-marked relative pronouns in the strict sense are almost entirely confined to European languages, where they are widespread except among the Celtic family and Indo-Aryan family. The influence of Spanish has led to their adaption by a very small number of Native American languages, of which the best-known are the Keresan languages.
Pronoun retention type
In this type, the position relativized is indicated by means of a personal pronoun in the same syntactic position as would ordinarily be occupied by a noun phrase of that type in the main clause — known as a resumptive pronoun. It is equivalent to saying “The man who I saw him yesterday went home”. Pronoun retention is very frequently used for relativization of inaccessible positions on the accessibility hierarchy. In Persian and Classical Arabic, for example, resumptive pronouns are required when the embedded role is other than the subject or direct object, and optional in the case of the direct object. Resumptive pronouns are common in non-verb-final languages of Africa and Asia, and also used by the Celtic languages of northwest Europe and Romanian (“Omul pe care l-am văzut ieri a mers acasă”/”The man who I saw him yesterday went home”). They also occur in deeply embedded positions in English, as in “That’s the girl that I don’t know what she did”, although this is sometimes considered non-standard.
Only a very small number of languages, of which the best known is Yoruba, have pronoun retention as their sole grammatical type of relative clause.
In the nonreduction type, unlike the other three, the shared noun occurs as a full-fledged noun phrase in the embedded clause, which has the form of a full independent clause. Typically, it is the head noun in the main clause that is reduced or missing. Some languages use relative clauses of this type with the normal strategy of embedding the relative clause next to the head noun. These languages are said to have internally headed relative clauses, which would be similar to the (ungrammatical) English structure “[You see the girl over there] is my friend” or “I took [you see the girl over there] out on a date”. This is used, for example, in Navajo, which uses a special relative verb (as with some other Native American languages).
A second strategy is the correlative-clause strategy used by Hindi and other Indo-Aryan languages, as well as Bambara. This strategy is equivalent to saying “Which girl you see over there, she is my daughter” or “Which knife I killed my friend with, the police found that knife”. It is “correlative” because of the corresponding “which … that …” demonstratives or “which … she/he/it …” pronouns, which indicate the respective nouns being equated. Note that the shared noun can either be repeated entirely in the main clause or reduced to a pronoun. Note also that there is no need to front the shared noun in such a sentence. For example, in the second example above, Hindi would actually say something equivalent “I killed my friend with which knife, the police found that knife”.
Dialects of some European languages, such as Italian, do use the nonreduction type in forms that could be glossed in English as “The man just passed us by, he introduced me to the chancellor here.” Similarly, spoken English tends to replace uses of the relative pronoun whose with non-reduced clauses. For example, consider the following sentence:
The man whose daughter I know is arriving tomorrow.
Informal English would tend to say instead
This man, I know his daughter, (and) he’s arriving tomorrow.
In general, however, nonreduction is restricted to verb-final languages, though it is more common among those that are head-marking.
Strategies for joining the relative clause to the main clause
The following are some of the common strategies for joining the two clauses:
- Use of an indeclinable particle (specifically, a complementizer) inserted into the sentence, placed next to the modified noun; the embedded clause is likewise inserted into the appropriate position, typically placed on the other side of the complementizer. This strategy is very common and arguably occurs in English with the word that (“the main that I saw”), though this interpretation of “that” as something other than a relative pronoun is controversial (see below). In the modern varieties of Arabic (using illi placed after the modified noun); in Chinese (using de placed before the modified noun); and in Japanese (using no placed before the modified noun).
- Use of a relative pronoun. Prototypically, a relative pronoun agrees with the head noun in gender, number, definiteness, animacy, etc., but adopts the case that the shared noun assumes in the embedded, not matrix, clause. This is the case in a number of conservative European languages, such as Latin, German and Russian. Many languages also have similar linking words common termed “relative pronouns” that agree in some way with the head noun, but do not adopt the case role of the embedded clause. In English, for example, the use of who vs. which agrees with the animacy of the head noun, but there is no case agreement except in the formal English contrast who vs. whom (which is often used incorrectly, if at all, in speech). Similarly, in Classical Arabic, there is a relative pronoun that agrees in number, gender, definiteness and case with the head noun (rather than taking the case role of the noun in the embedded clause). Languages with prototypical relative pronouns typically use the gapping strategy for indicating the role in the embedded clause, since the relative pronoun itself indicates the role by its case. (Classical Arabic, where the case marking indicates something else, uses a resumptive pronoun.) Some linguists prefer to use the term relative pronoun only for the prototypical cases (but in this case it’s unclear what to call the non-prototypical cases).
- Directly inserting the embedded clause in the matrix clause at the appropriate position, with no word used to join them. This is common, for example, in English (cf. “The man I saw yesterday went home”), and is used in Classical Arabic in relative clauses that modify indefinite nouns.
- By nominalizing the relative clause (e.g. converting it to a participial construction). Generally, no relative pronoun or complementizer is used. This occurs, for example, in reduced relative clauses in English (e.g. “The man seen by me yesterday went home” or “The man planning to go home soon is my friend”). Formal German makes common use of such participial relative clauses, which can become extremely long. This is also the normal strategy in Turkish, which has sentences equivalent to “I ate the potato of Hasan’s giving to Sina” (in place of “I ate the potato that Hasan gave to Sina”). Note that this can be viewed as a situation in which the “complementizer” is attached to the verb of the embedded clause (e.g. in English, “-ing” or “-ed” can be viewed as a type of complementizer).
Position of the head noun with respect to the relative clause
The positioning of a relative clause before or after a head noun is related to the more general concept of branching in linguistics. Languages that place relative clauses after their head noun (so-called head-initial or VO languages) generally also have adjectives and genitive modifiers following the head noun, as well as verbs preceding their objects. French, Spanish and Arabic are prototypical languages of this sort. Languages that place relative clauses before their head noun (so-called head-final or OV languages) generally also have adjectives and genitive modifiers preceding the head noun, as well as verbs following their objects. Turkish and Japanese are prototypical languages of this sort. Not all languages fit so easily into these categories. English, for example, is generally head-first, but has adjectives preceding their head nouns, and genitive constructions with both preceding and following modifiers (“the friend of my father” vs. “my father’s friend”). Chinese has the VO order, with verb preceding object, but otherwise is generally head-final.
Various possibilities for ordering are:
- Relative clause following the head noun, as in English, French or Arabic.
- Relative clause preceding the head noun, as in Turkish, Japanese, or Chinese.
- Head noun within the relative clause (an internally-headed relative clause). An example of such a language is Navajo. These languages are said to have nonreduced relative clauses. These languages have a structure equivalent to “[I saw the man yesterday] went home”.
- Adjoined relative clause. These languages have the relative clause completely outside the main clause, and use a correlative structure to link the two. These languages also have nonreduced relative clauses. Hindi is the most well known such language, and have a structure similar to “Which man I saw yesterday, that man went home” or (with non-fronting of the relativized noun in the relative clause) “I saw which man yesterday, that man went home”. Another example is Warlpiri, which constructs relative clauses of a form similar to “I saw the man yesterday, which he was going home”. However, it is sometimes said these languages have no relative clauses at all, since the sentences of this form can equally well translate as “I saw the man who was going home yesterday” or “I saw the man yesterday when/while he was going home”.
The antecedent of the relative clause (that is, the noun that is modified by it) can in theory be the subject of the main clause, or its object, or any other verb argument. In many languages, however, especially rigidly left-branching, dependent-marking languages with prenominal relative clauses, there are major restrictions on the role the antecedent may have in the relative clause.
Subject > Direct Object > Indirect Object > Oblique > Genitive > Object of comparative
Ergative–absolutive languages have a similar hierarchy:
This order is referred to as the accessibility hierarchy. If a language can relativize positions lower in the accessibility hierarchy, it can always relativize positions higher up, but not vice versa. For example, Malagasy can relativize only subject and Chukchi only absolutive arguments, whilst Basque can relativize absolutives, ergatives and indirect objects, but not obliques or genitives or objects of comparatives. Similar hierarchies have been proposed in other circumstances, e.g. for pronominal reflexes.
Languages which cannot relativize directly on noun phrases low in the accessibility hierarchy can sometimes use alternative voices to “raise” the relevant noun phrase so that it can be relativized. The most common example is the use of applicative voices to relativize obliques, but in such languages as Chukchi antipassives are used to raise ergative arguments to absolutive.
For example, a language that can relativize only subjects could say this:
- The girl [who likes me] came to visit.
- *The girl [who I like] came to visit.
- *The girl [who I gave a rose to] came to visit.
- *The girl [who I watched a movie with] came to visit.
- *The girl [whose father I know] came to visit.
- *The girl [who I know the father of] came to visit. (equivalent to previous)
- *The girl [who I am taller than] came to visit.
These languages might form an equivalent sentence by passivization:
- The girl [who was liked by me] came to visit.
- The girl [who was given a rose by me] came to visit.
- The girl [who was watched a movie with by me] came to visit.
- The girl [who was known the father of by me] came to visit.
- The girl [who was been taller than by me] came to visit.
Note that these passivized sentences get progressively more ungrammatical in English as they move down the accessibility hierarchy; the last two, in particular, are so ungrammatical as to be almost unparsable by English speakers. However, those languages with severe restrictions on which roles can be relativized are precisely those that can passivize almost any position, and hence the last two sentences would be normal in these languages.
A further example is languages that can relativize only subjects and direct objects. Hence the following would be possible:
- The girl [who I like] came to visit.
However, the other ungrammatical examples above would still be ungrammatical. These languages often allow an oblique object to be moved to the direct object slot by the use of the so-called applicative voice, similar to how the passive voice moves an oblique object to the subject position. The above examples expressed in an applicative voice might be similar to the following (in not necessarily grammatical English):
- The girl [who I gave a rose] came to visit.
- The girl [who I with-watched a movie] came to visit.
- The girl [who I (of-)know the father] came to visit.
- The girl [who I out-tall] came to visit.
Modern grammars may use the accessibility hierarchy to order productions — e.g. in Head-Driven Phrase Structure Grammar the hierarchy corresponds to the order of elements on the subcat list, and interacts with other principles in explanations of binding facts. The hierarchy also figures in Lexical Functional Grammar where it is known as Syntactic Rank or the Relational Hierarchy.