Valency

The number of arguments that a verb takes is called its ''valency'' or ''valence''. Verbs can be classified according to their valency:

Intransitive (valency = 1): the verb only has a subject. For example: "he runs", "it falls".

Transitive (valency = 2): the verb has a subject and a direct object. For example: "she eats fish", "Mike hunts deer".

Ditransitive (valency = 3): the verb has a subject, a direct object and an indirect or secondary object. For example: "I gave her a book," "She sent me flowers."

It is possible to have verbs with zero valency. Weather verbs are often impersonal (subjectless) in null-subject languages like Spanish, where the verb ''llueve'' means "It rains". In English, they require a dummy pronoun, and therefore formally have a valency of 1.The Tlingit language features a four way classification of verbs based on their valency. The intransitive and transitive are typical, but the impersonal and objective are somewhat different from the norm. In the objective the verb takes an object but no subject, the nonreferent subject in some uses may be marked in the verb by an incorporated dummy pronoun similar to the English weather verb (see below). Impersonal verbs take neither subject nor object, as with other null subject languages, but again the verb may show incorporated dummy pronouns despite the lack of subject and object phrases. Tlingit lacks a ditransitive, so the indirect object is described by a separate, extraposed clause.English verbs are often flexible with regard to valency. A transitive verb can often drop its object and become intransitive; or an intransitive verb can take an object and become transitive. Compare:

''I turned.'' (intransitive)

''I turned the car.'' (transitive)

In the first example, the verb ''turn'' has no grammatical object. (In this case, there may be an object understood - the subject (I/myself). The verb is then possibly reflexive, rather than intransitive); in the second the subject and object are distinct. The verb has a different valency, but the form remains exactly the same.

In many languages other than English, such valency changes aren't possible like this; the verb must instead be inflected for voice in order to change the valency.

Copula

A copula is a word that is used to describe its subject,or to equate or liken the subject with its predicate.In many languages, copulas are a special kind of verb, sometimes called ''copulative verbs'' or ''linking verbs''.

Because copulas do not describe actions being performed, they are usually analysed outside the transitive/intransitive distinction.The most basic copula in English is ''to be''; there are others (''remain'', ''seem'', ''grow'', ''become'', etc.).Some languages (the Semitic and Slavic families, Chinese, Sanskrit, and others) can omit or do not have the simple copula equivalent of "to be", especially in the present tense. In these languages a noun and adjective pair (or two nouns) can constitute a complete sentence. This construction is called ''zero copula''.

Verbal noun and verbal adjective

Most languages have a number of verbal nouns that describe the action of the verb. In Indo-European languages, there are several kinds of verbal nouns, including gerunds, infinitives, and supines. English has gerunds, such as ''seeing'', and infinitives such as ''to see''; they both can function as nouns; ''seeing is believing'' is roughly equivalent in meaning with ''to see is to believe.'' These terms are sometimes applied to verbal nouns of non-Indo-European languages.

In the Indo-European languages, verbal adjectives are generally called participles. English has an active participle, also called a present participle; and a passive participle, also called a past participle. The active participle of ''give'' is ''giving'', and the passive participle is ''given''. The active participle describes nouns that perform the action given in the verb, e.g. ''a giving person''.The passive participle describes nouns that have been the object of the action of the verb, e.g. ''given money''.Other languages apply tense and aspect to participles, and possess a larger number of them with more distinct shades of meaning.

Agreement

In languages where the verb is inflected, it often agrees with its primary argument (what we tend to call the subject) in person, number and/or gender. English only shows distinctive agreement in the third person singular, present tense form of verbs (which is marked by adding "-s"); the rest of the persons are not distinguished in the verb.

Spanish inflects verbs for tense/mood/aspect and they agree in person and number (but not gender) with the subject. Japanese, in turn, inflects verbs for many more categories, but shows absolutely no agreement with the subject. Basque, Georgian, and some other languages, have ''polypersonal agreement'': the verb agrees with the subject, the direct object and even the secondary object if present.

References

Gideon Goldenberg, "On Verbal Structure and the Hebrew Verb", in: idem, ''Studies in Semitic Linguistics'', Jerusalem: Magnes Press 1998, pp. 148-196 translation; originally published in Hebrew in 1985 .