Copula

The linguistic term copula in syntax and semantics refers to a word or phrase that links the sentence subject with a complement in the predicate (subject complement). For example, the be verb is serves as a copula in a sentence like The Earth is a planet. Copulas are used in most Western languages (except some like Russian) and in many other languages. It is usually a verb or similar type of word, and such verbs are called copular verbs, or informally, linking verbs. In some languages like Korean, it may take the form of a verb affixed to the complement noun. The word copula derives from the Latin word for "link" or "tie".

Most languages have one copula like the forms of to be in English. A few languages like Spanish have two: ser for more expressing essence or existential meanings (existence, inherent properties), and estar for expressing states of being, properties, and locations. In English and related languages, a few verbs have similar functions, like become, get, feel, seem, which are often also called linking verbs, but more technically are semi-copulas or pseudo-copulas.

1 Meanings and functions

1.1 General meanings

Predicate copula constructions can express identity, i.e., that the subject and predicate noun phrases are the same referent or express an identical concept.

• That star is Alpha Centauri.
• This is my dog.

They can express class inclusion, class membership, or subset relationships.

• Venus flytraps are insect-eating plants.
• Garfield is a famous cartoon cat.
• My dog is a Great Dane.
• She is an engineer.

They can express temporary or permanent properties or relations, that is, predication.

• The flowers are bright blue.
• I am your father.
• The students are confused.

They can express position or location.

• The van is by the river.

1.2 Non-copular uses

The be-verb in English and in many other languages expresses existence, which is less of a linking verb and more of a statement of existence.

• To be or not to be.
• I think, therefore I am.

Additionally, English copulas can form auxiliary constructions for progressive verb tenses, e.g., The squirrel is sleeping.

2 Zero copula

In some languages like Russian, Arabic and Hebrew, copular verbs are usually omitted, especially in the present tense. In English, the copula can be omitted in certain expressions that sound literary or poetic, especially expressions borrowed and translated from Latin. In Latin, copulas are usually expressed, but in short phrases that are not complete sentences, they are optional.

• The more, the better.
• The more, the merrier.
• Out of many, one. (from Latin E pluribus unum)

This poetic flavor shows up occasionally in a few colloquial or slang expressions.

• True that. (or: True, that.)

3 Pseudo-copulas

Other linking verbs include become, sensory verbs, verbs of appearance, feeling expressions, and verbs of location.

Become

• We grew up to become scientists.

Verbs of appearance or tendency

• This seems suspicious.
• This looks strange.
• They tend to act like that.

Locative verbs

• Hamburg stands on the Elbe River.

Sensory and feeling verbs

• The bread smells awful.
• This soup tastes so good.
• That sounds odd.
• My stomach feels really bad right now.

4 Forms

The English verb be is inflected in the various tenses as be, am, is, are, being, was, were, been. Some archaic forms seen in older texts include (thou) art, (thou) wast, (she) wert, and occasionally the old subjunctive beest.