copula verb

In linguistics, a copula (plural: copulas or copulae; abbreviated ) is a word or phrase that links the subject of a sentence to a subject complement, such as the word ''is'' in the sentence "The sky is blue" or the phrase ''was not being'' in the sentence "It was not being co-operative." The word ''copula'' derives from the Latin noun for a "link" or "tie" that connects two different things.

A copula is often a verb or a verb-like word, though this is not universally the case. A verb that is a copula is sometimes called a copulative or copular verb. In English primary education grammar courses, a copula is often called a linking verb. In other languages, copulas show more resemblances to pronouns, as in Classical Chinese and Guarani, or may take the form of suffixes attached to a noun, as in Korean, Beja, and Inuit languages.

Most languages have one main copula, although some (like Spanish, Portuguese and Thai) have more than one, while others have none. In the case of English, this is the verb ''to be''. While the term ''copula'' is generally used to refer to such principal verbs, it may also be used for a wider group of verbs with similar potential functions (like ''become'', ''get'', ''feel'' and ''seem'' in English); alternatively, these might be distinguished as "semi-copulas" or "pseudo-copulas".

Grammatical function

The principal use of a copula is to link the subject of a clause to a subject complement. A copular verb is often considered to be part of the predicate, the remainder being called a predicative expression. A simple clause containing a copula is illustrated below:

The book is on the table.

In that sentence, the noun phrase ''the book'' is the subject, the verb ''is'' serves as the copula, and the prepositional phrase ''on the table'' is the predicative expression. The whole expression ''is on the table'' may (in some theories of grammar) be called a predicate or a verb phrase.

The predicative expression accompanying the copula, also known as the complement of the copula, may take any of several possible forms: it may be a noun or noun phrase, an adjective or adjective phrase, a prepositional phrase (as above) or an adverb or another adverbial phrase expressing time or location. Examples are given below (with the copula in bold and the predicative expression in italics):

The three components (subject, copula and predicative expression) do not necessarily appear in that order: their positioning depends on the rules for word order applicable to the language in question. In English (an SVO language), the ordering given above is the normal one, but certain variation is possible:
*In many questions and other clauses with subject–auxiliary inversion, the copula moves in front of the subject: ''Are you happy?''
*In inverse copular constructions (see below) the predicative expression precedes the copula, but the subject follows it: ''In the room were three men.''

It is also possible, in certain circumstances, for one (or even two) of the three components to be absent:
*In null-subject (pro-drop) languages, the subject may be omitted, as it may from other types of sentence. In Italian, means ‘I am tired’, literally ‘am tired’.
*In non-finite clauses in languages like English, the subject is often absent, as in the participial phrase ''being tired'' or the infinitive phrase ''to be tired''. The same applies to most imperative sentences like ''Be good!''
*For cases in which no copula appears, see below.
*Any of the three components may be omitted as a result of various general types of ellipsis. In particular, in English, the predicative expression may be elided in a construction similar to verb phrase ellipsis, as in short sentences like ''I am''; ''Are they?'' (where the predicative expression is understood from the previous context).

Inverse copular constructions, in which the positions of the predicative expression and the subject are reversed, are found in various languages. They have been the subject of much theoretical analysis, particularly in regard to the difficulty of maintaining, in the case of such sentences, the usual division into a subject noun phrase and a predicate verb phrase.

Another issue is verb agreement when both subject and predicative expression are noun phrases (and differ in number or person): in English, the copula typically agrees with the syntactical subject even if it is not logically (i.e. semantically) the subject, as in ''the cause of the riot is'' (not ''are'') ''these pictures of the wall''. Compare Italian ; notice the use of the plural to agree with plural "these photos" rather than with singular "the cause". In instances where an English syntactical subject comprises a prepositional object that is pluralized, however, the prepositional object agrees with the predicative expression, e.g. "What kind ''of birds are'' those?"

The definition and scope of the concept of a copula is not necessarily precise in any language. As noted above, though the concept of the copula in English is most strongly associated with the verb ''to be'', there are many other verbs that can be used in a copular sense as well.
* The boy became a man.
* The girl grew more excited as the holiday preparations intensified.
* The dog felt tired from the activity.

And more tenuously
* The milk turned sour.
* The food smells good.
* You seem upset.

Meanings

Predicates formed using a copula may express identity: that the two noun phrases (subject and complement) have the same referent or express an identical concept:

They may also express membership of a class or a subset relationship:

Similarly they may express some property, relation or position, permanent or temporary:

Other special uses of copular verbs are described in some of the following sections.

Essence vs. state

Some languages use different copulas, or different syntax, to denote a permanent, essential characteristic of something versus a temporary state. For examples, see the sections on the Romance languages, Slavic languages and Irish.

Forms

In many languages the principal copula is a verb, like English ''(to) be'', German , Mixtec , Touareg ''emous'', etc. It may inflect for grammatical categories like tense, aspect and mood, like other verbs in the language. Being a very commonly used verb, it is likely that the copula has irregular inflected forms; in English, the verb ''be'' has a number of highly irregular ( suppletive) forms and has more different inflected forms than any other English verb (''am'', ''is'', ''are'', ''was'', ''were'', etc.; see English verbs for details).

Other copulas show more resemblances to pronouns. That is the case for Classical Chinese and Guarani, for instance. In highly synthetic languages, copulas are often suffixes, attached to a noun, but they may still behave otherwise like ordinary verbs: in Inuit languages.

In some other languages, like Beja and Ket, the copula takes the form of suffixes that attach to a noun but are distinct from the person agreement markers used on predicative verbs. This phenomenon is known as '' nonverbal person agreement'' (or ''nonverbal subject agreement''), and the relevant markers are always established as