In linguistics, conjugation () is the creation of derived forms of a verb from its principal parts by inflection (alteration of form according to rules of grammar). For instance, the verb break can be conjugated to form the words break, breaks, broke, broken and breaking. While English has a relatively simple conjugation, other languages such as French and Arabic are more complex, with each verb having dozens of conjugated forms. Some languages such as Georgian and Basque have highly complex conjugation systems with hundreds of possible conjugations for every verb.
Verbs may inflect for grammatical categories such as person, number, gender, case, tense, aspect, mood, voice, possession, definiteness, politeness, causativity, clusivity, interrogatives, transitivity, valency, polarity, telicity, volition, mirativity, evidentiality, animacy, associativity, pluractionality, and reciprocity. Verbs may also be affected by agreement, polypersonal agreement, incorporation, noun class, noun classifiers, and verb classifiers. Agglutinative and polysynthetic languages tend to have the most complex conjugations, albeit some fusional languages such as Archi can also have extremely complex conjugation. Typically the principal parts are the root and/or several modifications of it (stems). All the different forms of the same verb constitute a lexeme, and the canonical form of the verb that is conventionally used to represent that lexeme (as seen in dictionary entries) is called a lemma.
The term conjugation is applied only to the inflection of verbs, and not of other parts of speech (inflection of nouns and adjectives is known as declension). Also it is often restricted to denoting the formation of finite forms of a verb – these may be referred to as conjugated forms, as opposed to non-finite forms, such as the infinitive or gerund, which tend not to be marked for most of the grammatical categories.
Conjugation is also the traditional name for a group of verbs that share a similar conjugation pattern in a particular language (a verb class). For example, Latin is said to have 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. A verb that does not follow all of the standard conjugation patterns of the language is said to be an irregular verb. The system of all conjugated variants of a particular verb or class of verbs is called a verb paradigm; this may be presented in the form of a conjugation table.
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 (except in the subjunctive, as "They requested that she go with them"). 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, but 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 used only for emphasis or to clear ambiguity in complex texts.
Some languages have a richer agreement system in which verbs agree also 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 can exhibit agreement for the listener as the implicit benefactor: autoa ekarri digute means "they brought us the car" (neuter agreement for the 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, but 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 that 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 clitic 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 affixes 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:
Therefore, the person agreement affixes 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.
These common grammatical categories affect how verbs can be conjugated:
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. 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, Yiddish, Dutch, Afrikaans, Icelandic, Faroese, Swedish, Norwegian, Latvian, Bulgarian, Serbo-Croatian, Polish, Slovenian, Macedonian, Urdu or Hindi, Persian, Latin, French, Italian, Spanish, Portuguese, Russian, Albanian, Armenian, Irish, Ukrainian, 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.
One common feature of Pama–Nyungan languages, the largest family of Australian Aboriginal languages, is the notion of conjugation classes, which are a set of groups into which each lexical verb falls. They determine how a verb is conjugated for Tense–aspect–mood. The classes can but do not universally correspond to the transitivity or valency of the verb in question. Generally, of the two to six conjugation classes in a Pama-Nyungan language, two classes are open with a large membership and allow for new coinages, and the remainder are closed and of limited membership.
They are labelled by using common morphological components of verb endings in each respective class in infinitival forms. In the Wanman language these each correspond to la, ya, rra, and wa verbs respectively.
See also a similar table of verb classes and conjugations in Pitjantjatjara, a Wati language wherein the correlating verb classes are presented below also by their imperative verbal endings -la, -∅, -ra and -wa respectively
In the case of Ngarla, there is a notably strong correlation between conjugation class and transitivity, with transitive/ditransitive verbs falling in the l-class and intransitive/semi-transitive verbs in the ∅-class.
These classes even extend to how verbs are nominalized as instruments with the l-class verb including the addition of an /l/ before the nominalizing suffix and the blank class remaining blank:
Kunyjarta-lu mara ku-rnu parnu-nga warnta pirri-lpunyjarri, kurni-rnu kunyjarta kurri
‘(The) woman caused her digging stick to be in (the) hand (i.e. picked up her digging stick), (and) threw (it) at (the) girl.’
‘(A) match (lit. something to light with) give on (i.e. to) me, (a) fire I intend to light.’
Yidiny has a ternary verb class system with two open classes and one closed class (~20 members). Verbs are classified as: