In linguistics, conjugation is the creation of derived forms of a verb from its principal parts by inflection (regular alteration according to rules of grammar). Conjugation may be affected by person, number, gender, tense, aspect, mood, voice, or other grammatical categories. All the different forms of the same verb constitute a lexeme and the form of the verb that is conventionally used to represent the canonical form of the verb (one as seen in dictionary entries) is a lemma. Inflection of nouns and adjectives is known as declension.
Conjugated forms of a verb are called finite forms. In many languages there are also one or more forms that remain unchanged with all or most of grammatical categories: the non-finite forms, such as the infinitive or the gerund. A table giving all the conjugated variants of a verb in a given language is called a conjugation table or a verb paradigm.
A regular verb has a set of conventions for conjugation (paradigm) that derives all forms from a few specific forms or principal parts (maybe only one, such as the infinitive in English), in spelling or pronunciation. A verb that has conjugations deviating from this convention is said to be an irregular verb. Typically the principal parts are the root and/or several modifications of it (stems).
Conjugation is also the traditional name of a group of verbs that share a similar conjugation pattern in a particular language (a verb class). This is the sense in which teachers say that Latin has four conjugations of verbs. This means that any regular Latin verb can be conjugated in any person, number, tense, mood, and voice by knowing which of the four conjugation groups it belongs to, and its principal parts.
In Latin the present conjugation is o, s, t, mus, tis, nt, which respectively means I__, You (singular) __, He/she/it__, we__, you (plural)__, they__.Indo-European languages usually inflect verbs for several grammatical categories in complex paradigms, although some, like English, have simplified verb conjugation to a large extent. Afrikaans and Swedish have gone even further and virtually abandoned verb conjugation altogether. Below is the conjugation of the verb to be in the present tense (of the infinitive, if it exists, and indicative moods), in English, German, Dutch, Afrikaans, Icelandic, Swedish, Latvian, Bulgarian, Bosnian, Serbian, Croatian, Polish, Slovenian, Hindi, Persian, Latin, French, Italian, Spanish, Portuguese, Russian, Albanian, Armenian, Irish, Ancient Attic Greek and Modern Greek. This is usually the most irregular verb. The similarities in corresponding verb forms may be noticed. Some of the conjugations may be disused, like the English thou-form, or have additional meanings, like the English you-form, which can also stand for second person singular or be impersonal.
|Singular persons||Plural persons|
|Greek, Ancient (to 1453): εἶναι|
|Greek, Ancient (to 1453): εἰμί|
|Greek, Ancient (to 1453): εἶ|
|Greek, Ancient (to 1453): ἐστί|
|Greek, Ancient (to 1453): ἐσμέν|
|Greek, Ancient (to 1453): ἐστέ|
|Greek, Ancient (to 1453): εἰσί|
1Obsolete; used only with the obsolete pronoun 'thou'.
2In Flemish dialects.
4 'eínai' is only used as a noun ("being, existence").
5 Ptc: qenë.
6 In the Tosk and Geg dialects, respectively.
Verbal agreement or concord is a morpho-syntactic construct in which properties of the subject and/or objects of a verb are indicated by the verb form. Verbs are then said to agree with their subjects (resp. objects).
Many English verbs exhibit subject agreement of the following sort: whereas I go, you go, we go, they go are all grammatical in standard English, she go is not. Instead, a special form of the verb to go has to be used to produce she goes. On the other hand I goes, you goes etc. are not grammatical in standard English. (Things are different in some English dialects that lack agreement.) A few English verbs have no special forms that indicate subject agreement (I may, you may, she may), and the verb to be has an additional form am that can only be used with the pronoun I as the subject.
Verbs in written French exhibit more intensive agreement morphology than English verbs: je suis (I am), tu es ("you are", singular informal), elle est (she is), nous sommes (we are), vous êtes ("you are", plural), ils sont (they are). Historically, English used to have a similar verbal paradigm. Some historic verb forms are used by Shakespeare as slightly archaic or more formal variants (I do, thou dost, she doth, typically used by nobility) of the modern forms.
Some languages with verbal agreement can leave certain subjects implicit when the subject is fully determined by the verb form. In Spanish, for instance, subject pronouns do not need to be explicitly present, even though in French, its close relative, they are obligatory. The Spanish equivalent to the French je suis (I am) can be simply soy (lit. "am"). The pronoun yo (I) in the explicit form yo soy is only required for emphasis or to clear ambiguity in complex texts.
Some languages have a richer agreement system in which verbs also agree with some or all of their objects. Ubykh exhibits verbal agreement for the subject, direct object, indirect object, benefaction and ablative objects (a.w3.s.xe.n.t'u.n, you gave it to him for me).
Basque can show agreement not only for subject, direct object and indirect object, but it also on occasion exhibits agreement for the listener as the implicit benefactor: autoa ekarri digute means "they brought us the car" (neuter agreement for listener), but autoa ekarri ziguten means "they brought us the car" (agreement for feminine singular listener).
Languages with a rich agreement morphology facilitate relatively free word order without leading to increased ambiguity. The canonical word order in Basque is subject–object–verb. However, all permutations of subject, verb and object are permitted.
In some languages, predicative adjectives and copular complements receive a form of person agreement that is distinct from that used on ordinary predicative verbs. Although this is a form of conjugation in that it refers back to the person of the subject, it is not “verbal” because it always derives from pronouns that have become cliticised to the nouns to which they refer. An example of nonverbal person agreement, along with contrasting verbal conjugation, can be found from Beja (person agreement morphemes in bold):
In Turkic, and a few Uralic and Australian Aboriginal languages, predicative adjectives and copular complements take affixes that are identical to those used on predicative verbs, but their negation is different. For example, in Turkish:
but under negation this becomes (negative morphemes boldface):
For this reason, the person agreement morphemes used with predicative adjectives and nominals in Turkic languages are considered to be nonverbal in character. In some analyses, they are viewed as a form of verbal takeover by a copular strategy.
Common grammatical categories according to which verbs can be conjugated are the following:
Other factors which may affect conjugation are: