In linguistics, a copula (plural: copulas or copulae) is a word used to link the subject of a sentence with a predicate (a subject complement), such as the word is in the sentence "The sky is blue." 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 Beja, Ket, and Inuit languages.
Most languages have one main copula (although some, like Spanish and Thai, have more than one, and some 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 forms, it may also be used to refer to some other verbs with similar functions, like become, get, feel and seem in English (these may also be called "semi-copulas" or "pseudo-copulas").
Grammatical function 
The principal use of a copula is to link the subject of a clause to the predicate. 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 this English 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 for example be a noun or noun phrase, an adjective or adjective phrase, a prepositional phrase (as above) or another adverb or adverbial phrase expressing time or location. Examples are given below (with the copula in bold and the predicative expression in italics):
- 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 SVO language) the ordering given is the normal one, although here too 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, while 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. For example, in Italian, sono stanco means "I am tired", literally "am tired".
- In non-finite clauses 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 where no copula appears, see Zero copula 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. These 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 normally agrees with the preceding phrase, even if it is not logically the subject, as in the cause of the riot is (not are) these pictures of the wall. Compare Italian la causa della rivolta sono ("are", not è "is") queste foto del muro.
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:
- I only want to be myself.
- The Morning Star is the Evening Star.
They may also express membership of a class, or a subset relationship:
- She was a nurse.
- Dogs are carnivorous mammals.
Similarly they may express some property, relation or position, whether permanent or temporary:
- The trees are green.
- I am your boss.
- The hen is next to the cockerel.
- The children are confused.
Other special uses of copular verbs are described in some of the following sections.
Essence versus state 
Some languages use different copulas, or different syntax, when denoting a permanent, essential characteristic of something and when denoting a temporary state. For examples of this, see the sections below on the Romance languages, Slavic languages and Irish.
In many languages the principal copula is a verb, such as English (to) be, German sein, French être, etc. This may inflect for grammatical categories such as tense, aspect and mood, like other verbs in the language. As a very commonly used verb, it is likely that the copula will have irregular inflected forms; this is the case in English, where the verb be has a number of highly irregular (suppletive) forms, and in fact has a larger number of 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. This is the case for Classical Chinese and Guarani, for instance. In highly synthetic languages, copulas are often suffixes, attached to a noun, that may still behave otherwise like ordinary verbs, for example -u- in Inuit languages. In some other languages, such as 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 deriving from cliticized independent pronouns.
Additional uses of copular verbs 
A copular verb may also have other uses supplementary to or distinct from its uses as a copula.
As auxiliary verbs 
The English copular verb be can be used as an auxiliary verb, expressing passive voice (together with the past participle) or expressing progressive aspect (together with the present participle). For example:
- The man was killed. (passive)
- It is raining. (progressive)
Other languages' copulas also have uses as auxiliaries. For example, French être can be used to express passive voice similarly to English be, and both French être and German sein are used to express the perfect forms of certain verbs:
- Je suis venu. French for "I have come", literally "I am come."
This last usage was formerly prevalent in English also. The auxiliary functions of these verbs derive from their copular function, and can be interpreted as a special case of the copular function (the verbal form that follows it being considered adjectival).
Another auxiliary-type usage of the copula in English is together with the to-infinitive to denote an obligatory action or expected occurrence: "I am to serve you"; "The manager is to resign". This can also be put into past tense: "We were to leave at 9". For forms like "if I was/were to come", see English conditional sentences.
Existential usage 
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; I think therefore I am; 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.
Similar examples can be found in many other languages; for example, the French and Latin equivalents of I think therefore I am are Je pense, donc je suis and Cogito ergo sum, where suis and 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 Pienso, luego existo (where the verb existir "to exist" is used rather than the copula ser or estar "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 like the English there, while other languages use different verbs and constructions, like the French il y a (which uses parts of the verb avoir "to have", not the copula être) or the Swedish finns (the passive voice of the verb for "to find"). For details, see existential clause.
Zero copula 
In some languages, copula omission occurs within a particular grammatical context. For example, speakers of Russian, Hungarian, Arabic, Hebrew, and Quechuan languages consistently drop the copula in present tense: Russian: я — человек, ya — chelovek "I (am) a person"; Hungarian: ő ember, "s/he (is) a human"; Arabic: أنا إنسان ʔanā ʔinsān, "I (am) a human"; Hebrew: אני אדם ʔani ʔadam "I (am a) human"; Southern Quechua: payqa runam "s/he (is) a human". This usage is known generically as the zero copula. Note that in other tenses (sometimes in other persons besides third singular) the copula usually reappears.
In informal speech of English, the copula may be dropped. This is a feature of African American vernacular English but is also used by a variety of English speakers in informal contexts. An example: "Where you at? We at the store."
In Ancient Greek, when an adjective precedes a noun with an article, the copula is understood. Thus, ὁ οἴκος ἐστὶ μακρός, "the house is large," can be written μακρός ὁ οἴκος, "large the house (is)."
In Quechua —Southern Quechua used for the examples—, zero copula is restricted to present tense in third person singular only (kan): Payqa runam — "(s)he is a human"; but: (paykuna) runakunam kanku "(they) are human".
In Hungarian, zero copula is restricted to present tense in third person singular and plural: Ő ember/Ők emberek — "s/he is a human"/"they are humans"; but: (én) ember vagyok "I am a human", (te) ember vagy "you are a human", mi emberek vagyunk "we are humans", (ti) emberek vagytok "you (all) are humans". The copula also reappears for stating locations: az emberek a házban vannak, "the people are in the house," and for stating time: hat óra van, "it is six o'clock." However, the copula may optionally get omitted in colloquial language: hat óra (van), "it is six o'clock."
Hungarian uses a copula to say Itt van Róbert "Bob is here" (and this not only with regard to third person singular/plural), but not to say Róbert öreg "Bob is old". This is to relate a subject to a more temporary condition/state taking place in space (very often in the sense of Lojban zvati: la rabyrt. zvati ne'i le zdani "Robert is in the house").
Further restrictions may apply before omission is permitted. For example, in the Irish language, is, the present tense of the copula, may be omitted when the predicate is a noun. Ba the past/conditional cannot be deleted. If the present copula is omitted, the following pronoun é, í, iad preceding the noun is omitted as well.
Additional copulas 
Sometimes the term copula is taken to include not only a language's equivalent(s) to the verb be, but also other verbs or forms which serve to link a subject to a predicative expression (while adding semantic content of their own). For example, English verbs such as become, get, feel, look and seem can have this function, as in the following sentences (where the predicative expression – the complement of the verb – is in italics):
- She became a student.
- They look tired.
(This usage should be distinguished from the use of some of these verbs as "action" verbs, as in They look at the wall, where look denotes an action and cannot be replaced by the basic copula are.)
Some verbs have rarer, secondary uses as copular verbs, such as the verb fall in sentences like The zebra fell victim to the lion.
Copulas in particular languages 
The English copular verb be has eight forms (more than any other English verb): be, am, is, are, being, was, were, been. Additional archaic forms include art, wast, wert, and occasionally beest (as a subjunctive). For more details see English verbs. For the etymology of the various forms, see Indo-European copula.
The main uses of the copula in English are described in the above sections. The possibility of copula omission is mentioned under Zero copula.
A particular construction found in English (particularly in speech) is the use of two successive copulas when only one is necessary, as in My point is, is that... (the acceptability of this construction is one of the disputed matters in English grammar). For more information see Double copula.
In Indo-European languages, the words meaning to be are sometimes similar to each other. Due to the high frequency of their use, their inflection retains a considerable degree of similarity in some cases. Thus, for example, the English form is is a cognate of German ist, Latin est and Russian jest', even though the Germanic, Italic and Slavic language groups split at least 3000 years ago. The origins of the copulas of most Indo-European languages can be traced back to four Proto-Indo-European stems: *es- (*h1es-), *sta- (*steh2-), *wes- and *bhu- (*bʰuH-).
As in English, the verb "to be" (qopna) is irregular in Georgian (a Kartvelian language); different verb roots are employed in different tenses. The roots -ar-, -kn-, -qav-, and -qop- (past participle) are used in the present tense, future tense, past tense and the perfective tenses respectively. Examples:
Masc'avlebeli var. "I am a teacher." Masc'avlebeli viknebi. "I will be a teacher." Masc'avlebeli viqavi. "I was a teacher." Masc'avlebeli vqopilvar. "I have been a teacher." Masc'avlebeli vqopiliqavi. "I had been a teacher."
Note that, in the last two examples (perfective and pluperfect), two roots are used in one verb compound. In the perfective tense, the root qop (which is the expected root for the perfective tense) is followed by the root ar, which is the root for the present tense. In the pluperfective tense, again, the root qop is followed by the past tense root qav. This formation is very similar to German (an Indo-European language), where the perfect and the pluperfect are expressed in the following way:
Ich bin Lehrer gewesen. "I have been a teacher", literally "I am teacher been." Ich war Lehrer gewesen. "I had been a teacher", literally "I was teacher been."
Here, gewesen is the past participle of sein ("to be") in German. In both examples, as in Georgian, this participle is used together with the present and the past forms of the verb in order to conjugate for the perfect and the pluperfect aspects.
Copulas in the Romance languages usually consist of two different verbs that can be translated as "to be", the main one from the Latin esse (via Vulgar Latin essere; esse deriving from *es-), often referenced as sum, another of the Latin verb's principal parts), and a secondary one from stare (from *sta-), often referenced as sto, another of that Latin verb's principal parts. The resulting distinction in the modern forms is found in all the Iberian Romance languages, and to a lesser extent Italian, but not in French or Romanian. The difference is that the first usually refers to essential characteristics, while the second refers to states and situations, e.g., "Bob is old" versus "Bob is well". A similar division is found in the non-Romance Basque language (viz. egon and izan). (Note that the English words just used, "essential" and "state", are also cognate with the Latin infinitives esse and stare. The word "stay" also comes from Latin stare, through Middle French "estai", stem of Old French "ester".) In Spanish and Portuguese, the high degree of verbal inflection, plus the existence of two copulas (ser and estar), means that there are 105 (Spanish) and 110 (Portuguese) separate forms to express the copula, compared to eight in English and one in Chinese.
|Sum-derived||Bob è vecchio.||Bob es viejo.||"Bob is old."|
|Sto-derived||Bob sta bene.||Bob está bien.||"Bob is well."|
In some cases, the verb itself changes the meaning of the adjective/sentence. The following examples are from Portuguese:
|Copula||Example 1||Example 2|
|Sum-derived||O Bob é bom.||"Bob is good."||O Bob é parvo.||"Bob is foolish."|
|Sto-derived||O Bob está bem.||"Bob is feeling well."||O Bob está parvo.||"Bob is acting/being silly."|
Some Slavic languages make a distinction between essence and state (similar to that discussed in the above section on the Romance languages), by putting a predicative expression denoting a state into the instrumental case, while essential characteristics are in the nominative. This can apply with other copula verbs as well (e.g. the verbs for "become" are normally used with the instrumental).
In Irish and Scottish Gaelic, not only are there two copulas but the syntax is also changed when one is distinguishing between states or situations and essential characteristics. Describing the subject's state or situation typically uses the normal VSO ordering with the verb bí. The copula is, which is used to state essential characteristics or equivalences, requires a change in word order so that the subject does not immediately follow the copula (see Irish syntax).
In Irish, the copula is used for things that are in a permanent state.
Is fear Liam "Liam is a man" (lit., is man Liam) Is leabhar é sin "That is a book" (lit., is book it that)
The word "is" is the copula (rhymes with the English word "hiss"). The pronoun used with the copula is different from the normal pronoun. For a masculine singular noun, "é" is used (for "he" or "it"), as opposed to the normal pronoun "sé"; for a feminine singular noun, "í" is used (for "she" or "it"), as opposed to normal pronoun "sí"; for plural nouns, "iad" is used (for "they" or "those"), as opposed to the normal pronoun "siad".
To describe non-permanent states, "to be" is used, e.g., Tá mé ag rith "I am running".
Haitian Creole 
Haitian Creole, a French-based creole language, has three forms of the copula: se, ye, and the zero copula, no word at all (the position of which will be indicated with Ø, just for purposes of illustration).
Although no textual record exists of Haitian-Creole at its earliest stages of development from French, se is derived from French [se] (written c'est), which is the normal French contraction of [sə] (that, written ce) and the copula [e] (is, written est) (a form of the verb être).
The derivation of ye is less obvious; but we can assume that the French source was [ile] ("he/it is", written il est), which, in rapidly spoken French, is very commonly pronounced as [je] (typically written y est).
The use of a zero copula is unknown in French, and it is thought to be an innovation from the early days when Haitian-Creole was first developing as a Romance-based pidgin. Latin also sometimes used a zero copula.
Which of se / ye / Ø is used in any given copula clause depends on complex syntactic factors that we can superficially summarize in the following four rules:
1. Use Ø (i.e., no word at all) in declarative sentences where the complement is an adjective phrase, prepositional phrase, or adverb phrase:
Li te Ø an Ayiti. "She was in Haiti." (she past-tense in Haiti) Liv-la Ø jon. "The book is yellow." (book-the yellow) Timoun-yo Ø lakay. "The kids are [at] home." (kids-the home)
2. Use se when the complement is a noun phrase. But note that, whereas other verbs come after any tense/mood/aspect particles (like pa to mark negation, or te to explicitly mark past tense, or ap to mark progressive aspect), se comes before any such particles:
Chal se ekriven. "Charles is writer." Chal se pa ekriven. "Charles is not writer." cf. with the verb kouri ("run"): Chal pa kouri, not Chal kouri pa. Chal, ki se ekriven, pa vini. "Charles, who is writer, not come."
3. Use se where French and English have a dummy "it" subject:
Se mwen! "It's me!" French C'est moi! Se pa fasil. "It's not easy," colloquial French C'est pas facile.
4. Finally, use the other copula form ye in situations where the sentence's syntax leaves the copula at the end of a phrase:
Kijan ou ye? "How you are?" Pou kimoun liv-la te ye? "Whose book was it?" (of who book-the past-tense is?) M pa konnen kimoun li ye. "I don't know who he is." (I not know who he is) Se yon ekriven Chal ye. "Charles is a writer!" (it's a writer Charles is; cf. French C'est un écrivain qu'il est.)
Japanese has copulas that would most often be translated as one of the so-called be-verbs of English.
The Japanese copula has many forms. The words da and desu are used to predicate sentences, while na and de are particles used within sentences to modify or connect.
Japanese sentences with copulas most often equate one thing with another, that is, they are of the form "A is B." Examples:
私は学生だ。 Watashi wa gakusei da. "I'm a student." (lit., I TOPIC student COPULA) これはペンです。 Kore wa pen desu. "This is a pen." (lit., this TOPIC pen COPULA-POLITE)
The difference between da and desu appears simple. For instance desu is more formal and polite than da. Thus, many sentences such as the ones below are almost identical in meaning and differ in the speaker's politeness to the addressee and in nuance of how assured the person is of their statement. However, desu may never come before the end of a sentence, and da is used exclusively to delineate subordinate clauses. In addition, da is always declarative, never interrogative.
あれはホテルだ。 Are wa hoteru da. "That's a hotel." (lit., that TOPIC hotel COPULA) あれはホテルです。 Are wa hoteru desu. "That is a hotel." (lit., that TOPIC hotel COPULA-POLITE)
Japanese sentences may be predicated with copulas or with verbs. However, desu may not always be a predicate. In some cases, its only function is to make a sentence predicated with a stative verb more polite. However, da always functions as a predicate, so it cannot be combined with a stative verb, because sentences need only one predicate. See the examples below.
このビールはおいしい。 Kono bīru wa oishii. "This beer is delicious." (lit., this beer TOPIC be-tasty) このビールはおいしいです。 Kono bīru wa oishii desu. "This beer is good." (lit., this beer TOPIC be-tasty POLITE) *このビールはおいしいだ。 *Kono bīru wa oishii da. This is unacceptable because da may only serve as a predicate.
There are several theories as to the origin of desu; one is that it is a shortened form of であります de arimasu, which is a polite form of である de aru. In general, both forms are used in only writing and more formal situations. Another form, でございます de gozaimasu, which is the more formal version of de arimasu, in the etymological sense a conjugation of でござる de gozaru and an honorific suffix -ます -masu, is also used in some situations and is very polite. Note that de aru and de gozaru are considered to be compounds of a particle で de, and existential verbs aru and gozaru. です desu may be pronounced っす ssu in colloquial speech. The copula is subject to dialectal variation throughout Japan, resulting in forms such as や ya (in Kansai) and じゃ ja (in Hiroshima).
Japanese also has two verbs corresponding to English "to be": aru and iru. They are not copulas but existential verbs. Aru is used for inanimate objects, including plants, whereas iru is used for animate things like people, animals, and robots, though there are exceptions to this generalization.
本はテーブルにある。 Hon wa tēburu ni aru. "The book is on a table." キムさんはここにいる。 Kimu-san wa koko ni iru. "Kim is here."
For sentences with predicate nominatives, the copula "이다" (i-da) is added to the predicate nominative (with no space in between).
바나나는 과일이다. Ba-na-na-neun gwa-il-i-da.. "Bananas are a fruit."
Some adjectives (usually color adjectives) are nominalized and used with the copula "이다".
1. Without the copula "이다":
바나나는 노랗다. ba-na-na-neun no-rat-da.. "Bananas are yellow."
2. With the copula "이다":
바나나는 노란색이다. ba-na-na-neun no-ran-saek-i-da.. "Bananas are yellow-coloured."
Some Korean adjectives are derived using the copula. Separating these articles and nominalizing the former part will often result in a sentence with a related, but different meaning. Using the separated sentence in a situation where the un-separated sentence is appropriate is usually acceptable as the listener can decide what the speaker is trying to say using the context.
아이스크림은 맛있다. A-i-seu-keu-rim-eun mash-it-da.. "Ice cream is delicious" (The word delicious is derived from "has-flavor") 아이스크림은 맛이 있다. A-i-seu-keu-rim-eun mash-i it-da.. "Ice cream has flavor"
The opposite, ice cream is unappetizing, uses the Korean word "없다" (eopt-da), meaning "to not have".
아이스크림은 맛없다. A-i-seu-keu-rim-eun mat-eopt-da.. "Ice cream is unappetizing" (The word unappetizing is derived from "doesn't-have-flavor") 아이스크림은 맛이 없다. A-i-seu-keu-rim-eun mash-i eopt-da.. "Ice cream doesn't have flavor"
In Chinese languages, both states and qualities are, in general, expressed with stative verbs (SV) with no need for a copula, e.g., in Mandarin, "to be tired" (累 lèi), "to be hungry" (饿 è), "to be located at" (在 zài), "to be stupid" (笨 bèn) and so forth. These verbs are usually preceded by an adverb such as 很 hěn ("very") or 不 bù ("not"). A sentence could also simply use a pronoun and a verb: for example, 我饿。 wǒ è. "I am hungry." See also Chinese adjectives.
Only sentences with a noun as the complement (e.g., "this is my sister") use the verb "to be": 是 shì. This is used frequently: For example, instead of having a verb meaning "to be Chinese", the usual expression is "to be a Chinese person", using 是 shì. Some scholars call this verb form an equative verb (EV), as published in some Yale Chinese textbooks.
The history of the Chinese copula 是 is a controversial subject. Before the Han Dynasty, the character served as a demonstrative pronoun meaning "this" (this usage survives in some idioms and proverbs, as well as in Japanese). Some linguists argue that 是 developed into a copula because it often appeared, as a repetitive subject, after the subject of a sentence (in classical Chinese we can say, for example: "George W. Bush, this president of the United States" meaning "George W. Bush is the president of the United States). Other scholars do not completely accept the explanation, proposing that 是 served as a demonstrative pronoun and a copula at the same time in ancient Chinese. Etymologically, 是 developed from the meaning of "straight"; in modern Chinese, however, it can be combined with the modifier 的 de to mean "yes" or to show agreement. e.g. Question: 你的汽车是不是红色的？ nǐ de qìchē shì bú shì hóngsè de? "Is your car red or not?" Response: 是的。 shì de. "Is.", meaning "Yes.", or 不是。 bú shì. "Not is.", meaning "No." A more common way of showing that the person asking the question is correct is by simply saying "right" or "correct", 对 duì, which drops the modifier 的 de; the corresponding negative answer is 不对 bú duì, "Not right."
Siouan languages 
In Siouan languages like Lakota, in principle almost all words — according to their structure — are verbs. So not only (transitive, intransitive and so-called 'stative') verbs but even nouns often behave like verbs and do not need to have copulas.
For example, the word wičháša refers to a man, and the verb "to-be-a-man" is expressed as wimáčhaša/winíčhaša/wičháša (I am/you are/he is a man). Yet there also is a copula héčha (to be a ...) that in most cases is used: wičháša hemáčha/heníčha/héčha (I am/you are/he is a man).
In order to express the statement "I am a doctor of profession," one has to say pezuta wičháša hemáčha. But, in order to express that that person is THE doctor (say, that had been phoned to help), one must use another copula iyé (to be the one): pežúta wičháša (kiŋ) miyé yeló (medicine-man DEF ART I-am-the-one MALE ASSERT).
In order to refer to space (e.g., Robert is in the house), various verbs are used, e.g., yaŋkÁ (lit.: to sit) for humans, or háŋ/hé (to stand upright) for inanimate objects of a certain shape. "Robert is in the house" could be translated as Robert thimáhel yaŋké (yeló), whereas "there's one restaurant next to the gas station" translates as "owótethipi wígli-oínažiŋ kiŋ hél isákhib waŋ hé".
Constructed languages 
The constructed language Lojban has copulas, but they are rarely used, and are sometimes viewed with distaste in the Lojban community, because all words that express a predicate can be used as verbs. The three sentences "Bob runs", "Bob is old", and "Bob is a fireman", for instance, would all have the same form in Lojban: la bob. bajra, la bob. tolcitno, and la bob. fagdirpre. There are several different copulas: me turns whatever follows the word me into a verb that means to be what it follows. For example, me la bob. means to be Bob. Another copula is du, which is a verb that means all its arguments are the same thing (equal).
The E-Prime language, based on English, simply avoids the issue by not having a generic copula. It requires instead a specific form such as "remains", "becomes", "lies", or "equals".
Esperanto uses the copula much as English. The infinitive is esti, and the whole conjugation is regular (as with all Esperanto verbs). In addition, adjectival roots can be turned into stative verbs: La ĉielo bluas. "The sky is blue."
Likewise, Ido has a copula that works as English "to be". Its infinitive is esar, and, as is the case in Esperanto, all of its forms are regular: The simple present is esas for all persons; the simple past is esis, the simple future is esos, and the imperative is esez, among a few more forms. However, Ido also has an alternative irregular form for the simple present ("es"), which some Idists frown upon. The possibility to turn adjectives and even nouns into verbs also exist, although this is mostly done by means of an affix, on top of the verbal endings. The affix is "-es-". So, "The sky is blue." can be said as "La cielo bluesas". As can be seen, the suffix "-es-" plus the verbal desinence "-as" are simply the verb "to be" annexed to the adjectival or nominal root.
Interlingua speakers use copulas with the same freedom as speakers of Slavic, Germanic, and Romance languages. In addition to combinations with esser ('to be'), expressions such as cader prede ('to fall prey') are common. Esser is stated, rather than omitted as in Russian.
See also 
- See the appendix to Moro 1997 and the references cited there for a short history of the copula.
- Pustet, Regina (2005). Copulas: Universals in the Categorization of the Lexicon. Oxford studies in typology and linguistic theory. Oxford University Press. ISBN 0-19-928180-7.
- See Everaert et al. 2006.
- Stassen, Leon (1997). Intransitive Predication. Oxford studies in typology and linguistic theory. Oxford University Press. p. 39. ISBN 978-0-19-925893-2.
- Kneale - Kneale 1962 and Moro 1997
- 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.
- Bender, Emily (2000) Syntactic Variation and Linguistic Competence: The Case of AAVE Copula Absence. Ph.D. Dissertation, Stanford University
- C.S. Butler, Structure and Function: A Guide to the Three Major Structural-Functional Theories, John Benjamins Publishing, 2003, pp. 425–426.
- Myles Dillon and Donncha ó Cróinín, Irish, Teach Yourself Books, Saint Paul's House, Warwick Lane London EC4. Lesson VIII, "The Copula", p. 52
- Howe 1990. Source for most of the Haitian data in this article; for more details on syntactic conditions as well as Haitian-specific copula constructions, such as se kouri m ap kouri (It's run I progressive run; "I'm really running!"), see the grammar sketch in this publication.
- Valdman & Rosemond 1988.
- Sayuri Kusutani (Fall 2006). "The English Copula Be: Japanese Learners’ Confusion" (PDF). TESL Working Paper Series 4 (2).
- Pulleyblank, Edwin G. (1995). Outline of Classical Chinese Grammar. Vancouver: UBC Press. ISBN 0-7748-0541-2.
- Lojban For Beginners
- Bram, Barli (5 July 1995). Write Well: Improving Writing Skills. Yogyakarta, Indonesia: Penerbit Kanisius. p. 128. ISBN 978-979-497-378-3.
- Everaert, Martin; van Riemsdijk, Henk (eds.) (2006). The Blackwell Companion to Syntax, Volumes I-V (illustrated, revised ed.). Wiley-Blackwell. p. 849. ISBN 978-1-4051-1485-1. (See "copular sentences" and "existential sentences and expletive there" in Volume II.)
- Howe, Catherine; Desmarattes, Jean Lionel (1990). Haitian Creole Newspaper Reader. Dunwoody Press. p. 232. ISBN 978-0-931745-59-1.
- Kneale, William and Martha (1962). The Development of Logic. Oxford: Clarendon Press. ISBN 0-19-824183-6. OCLC 373178.
- Smith, Ron F; O'Connell, Loraine M. (March 2003). Editing Today Workbook (2nd ed.). Wiley-Blackwell. p. 264. ISBN 978-0-8138-1317-2.
- Moro, A. (1997) The raising of predicates. Cambridge University Press, Cambridge, England.
- Tüting, A. W. (December 2003). Essay on Lakota syntax.
- Valdman, Albert; Rosemond, Renote (1988). Ann Pale Kreyòl: An Introductory Course in Haitian Creole. Illustrations: Philippe, Pierre-Henri (Illustrated ed.). Creole Institute, Indiana University. ISBN 978-0-929236-00-1.