Editing Copula (linguistics) (section)

== Grammatical function ==
The principal use of a copula is to link the [[subject (grammar)|subject]] of a [[clause (grammar)|clause]] to a [[subject complement]]. A copular verb is often considered to be part of the [[predicate (grammar)|predicate]], the remainder being called a [[predicative expression]]. A simple clause containing a copula is illustrated below:

<blockquote>The book '''is''' on the table.</blockquote>

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. In some theories of grammar, the whole expression ''is on the table'' may be called a predicate or a [[verb phrase]].

The predicative expression accompanying the copula, also known as the [[complement (grammar)|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:

{{Poem quote|
Mary and John '''are''' ''my friends''.
The sky '''was''' ''blue''.
I '''am''' ''taller than most people''.
The birds and the beasts '''were''' ''there''.
}}

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 [[subject-verb-object|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 language|null-subject]] (pro-drop) languages, the subject may be omitted, as it may from other types of sentence. In [[Italian language|Italian]], {{lang|it|sono stanco}} means {{gloss|I am tired}}, literally {{gloss|am tired}}.
*In [[non-finite clause]]s in languages such as 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 such as ''Be good!''
*For cases in which no copula appears, see {{slink||Zero copula}} below.
*Any of the three components may be omitted as a result of various general types of [[ellipsis (grammar)|ellipsis]]. In particular, in English, the predicative expression may be elided in a construction similar to [[verb phrase ellipsis]], as in short sentences such as ''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.<ref>See Everaert et al. 2006.</ref> 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 [[agreement (linguistics)|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. [[semantics|semantically]]) the subject, as in ''the cause of the riot '''is''''' (not ''are'') ''these pictures of the wall''. Compare Italian {{lang|it|la causa della rivolta '''sono''' queste foto del muro}}; notice the use of the plural {{lang|it|sono}} to agree with plural {{lang|it|queste foto}} {{gloss|these photos}} rather than with singular {{lang|it|la causa}} {{gloss|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.<ref name="Givon">{{Cite book | title=English Grammar: A function-based introduction | volume=1 | author=Givón, T. | publisher=John Benjamins Publishing Company | year=1993 | url=https://books.google.com/books?id=TWZM1bFFMSkC | pages=103–104| isbn=9027273898 }}</ref><ref name="EG">{{Cite web | title=What are copular verbs? | url=https://www.englishgrammar.org/copular-verbs/ | date=November 15, 2010 | access-date=October 31, 2017 | archive-url=https://web.archive.org/web/20171107014423/https://www.englishgrammar.org/copular-verbs/ | archive-date=November 7, 2017 | url-status=dead }}</ref>
* 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<ref name="Givon" /><ref name="EG" />
* The milk '''turned''' sour.
* The food '''smells''' good.
* You '''seem''' upset.

=== Other functions ===
A copular verb may also have other uses supplementary to or distinct from its uses as a copula. Some co-occurrences are common.

==== Auxiliary verb ====
The English verb ''[[wikt:be#Verb|to be]]'' is also used as an [[English auxiliaries|auxiliary verb]], especially for expressing [[passive voice]] (together with the [[past participle]]) or expressing [[progressive aspect]] (together with the [[present participle]]):

{{Poem quote|
The man '''was''' killed. (passive)
It '''is''' raining. (progressive)
}}

Other languages' copulas have additional uses as auxiliaries. For example, French {{lang|fr|être}} can be used to express passive voice similarly to English ''be''; both French {{lang|fr|être}} and German {{lang|de|sein}} are used to express the [[Perfect (grammar)|perfect forms]] of certain verbs:

{{Poem quote|{{lang|fr|Je '''suis''' allé(e)}} French for {{gloss|I went}} and {{gloss|I have gone}}, literally {{gloss|I am gone}}, but does not imply still being gone.}}

In the same way, usage of English ''be'' in the present perfect, though archaic, is still commonly seen in old texts/translations:

{{Poem quote|
I '''am''' become death.
He '''is''' risen.
}}

The auxiliary functions of these verbs derived from their copular function, and could be interpreted as special cases of the copular function (with the verbal forms it precedes being considered adjectival).<!-- This sentence needs revision in order to be readily comprehended. -->

Another auxiliary usage in English is to denote an obligatory action or expected occurrence: "I am to serve you". "The manager is to resign". This can be put also into past tense: "We were to leave at 9". For forms such as "if I was/were to come", see [[English conditional sentences]]. (By certain criteria, the English copula ''be'' may always be considered an auxiliary verb; see [[Auxiliary verb#Diagnostics for identifying auxiliary verbs in English|Diagnostics for identifying auxiliary verbs in English]].)

==== Existential verb ====
The English ''to be'' and its equivalents in certain other languages also have a non-copular use as an existential verb, meaning "to exist". This use is illustrated in the following sentences: ''I want only '''to be''', and that is enough''; ''[[Cogito ergo sum|I think therefore I '''am''']]''; ''[[To be, or not to be|'''To be''' or not '''to be''']], that is the question.'' In these cases, the verb itself expresses a predicate (that of [[existence]]), rather than linking to a predicative expression as it does when used as a copula. In [[ontology]] it is sometimes suggested that the "is" of existence is reducible to the "is" of property attribution or class membership; to be, [[Aristotle]] held, is to be ''something''. However, [[Abelard]] in his ''Dialectica'' made a ''[[reductio ad absurdum]]'' argument against the idea that the copula can express existence.<ref>Kneale – Kneale 1962 and Moro 1997</ref>

Similar examples can be found in many other languages; for example, the French and Latin equivalents of ''I think therefore I am'' are {{lang|fr|Je pense, donc je '''suis'''}} and {{lang|la|Cogito ergo '''sum'''}}, where {{lang|fr|suis}} and {{lang|la|sum}} are the equivalents of English "am", normally used as copulas. However, other languages prefer a different verb for existential use, as in the Spanish version {{lang|es|Pienso, luego '''existo'''}} (where the verb {{lang|es|existir}} {{gloss|to exist}} is used rather than the copula {{lang|es|ser}} or {{lang|es|estar}} {{gloss|to be}}).

Another type of existential usage is in clauses of the ''[[there is]]...'' or ''there are...'' type. Languages differ in the way they express such meanings; some of them use the copular verb, possibly with an [[expletive pronoun]] such as the English ''there'', while other languages use different verbs and constructions, such as the French {{lang|fr|il y a}} (which uses parts of the verb {{lang|fr|avoir}} {{gloss|to have}}, not the copula) or the Swedish {{lang|sv|finns}} (the passive voice of the verb for "to find"). For details, see [[existential clause]].

Relying on a unified theory of copular sentences, it has been proposed that the English ''there''-sentences are subtypes of [[inverse copular construction]]s.<ref>See Moro 1997, and "existential sentences and expletive ''there''" in Everaert et al. 2006, for a detailed discussion of this issue and a historical survey of the major proposals.</ref>