Infinitive

Infinitive is a term in linguistics for certain verb forms existing in many languages, most often used as non-finite verbs that do not show a tense. As with many linguistic concepts, there is not a single definition applicable to all languages. The name is derived from Late Latin infinitivus, a derivative of infinitus meaning.
In traditional descriptions of English, the infinitive is the basic dictionary form of a verb when used non-finitely, with or without the particle to. Thus to go is an infinitive, as is go in a sentence like "I must go there". The form without to is called the bare infinitive, and the form with to is called the full infinitive or to-infinitive.
In many other languages the infinitive is a distinct single word, often with a characteristic inflective ending, like cantar in Portuguese, morir in Spanish, manger in French, portare in Latin and Italian, lieben in German, читать in Russian, etc. However, some languages have no infinitive forms. Many Native American languages, Arabic, Asian languages such as Japanese, and some languages in Africa and Australia do not have direct equivalents to infinitives or verbal nouns. Instead, they use finite verb forms in ordinary clauses or various special constructions.
Being a verb, an infinitive may take objects and other complements and modifiers to form a verb phrase. Like other non-finite verb forms, infinitives do not generally have an expressed subject; thus an infinitive verb phrase also constitutes a complete non-finite clause, called an infinitive clause. Such phrases or clauses may play a variety of roles within sentences, often being nouns, and sometimes being adverbs or other types of modifier. Many verb forms known as infinitives differ from gerunds in that they do not inflect for case or occur in adpositional phrases. Instead, infinitives often originate in earlier inflectional forms of verbal nouns. Unlike finite verbs, infinitives are not usually inflected for tense, person, etc. either, although some degree of inflection sometimes occurs; for example Latin has distinct active and passive infinitives.

Phrases and clauses

An infinitive phrase is a verb phrase constructed with the verb in infinitive form. This consists of the verb together with its objects and other complements and modifiers. Some examples of infinitive phrases in English are given below – these may be based on either the full infinitive or the bare infinitive.

sleep
write ten letters
go to the store for a pound of sugar

Infinitive phrases often have an implied grammatical subject making them effectively clauses rather than phrases. Such infinitive clauses or infinitival clauses, are one of several kinds of non-finite clause. They can play various grammatical roles like a constituent of a larger clause or sentence; for example it may form a noun phrase or adverb. Infinitival clauses may be embedded within each other in complex ways, like in the sentence:

I want to tell you that John Welborn is going to get married to Blair.

Here the infinitival clause to get married is contained within the finite dependent clause that John Welborn is going to get married to Blair; this in turn is contained within another infinitival clause, which is contained in the finite independent clause.
The grammatical structure of an infinitival clause may differ from that of a corresponding finite clause. For example, in German, the infinitive form of the verb usually goes to the end of its clause, whereas a finite verb typically comes in second position.

Clauses with implicit subject in the objective case

Following certain verbs or prepositions, infinitives commonly do have an implicit subject, e.g.,

I want them to eat their dinner.
For him to fail now would be a disappointment.

As these examples illustrate, the implicit subject of the infinitive occurs in the objective case in contrast to the nominative case that occurs with a finite verb, e.g., "They ate their dinner."
Such accusative and infinitive constructions are present in Latin and Ancient Greek, as well as many modern languages. The atypical case regarding the implicit subject of an infinitive is an example of exceptional case-marking. As shown in the above examples, the object of the transitive verb want and the preposition for allude to their respective pronouns' subjective role within the clauses.

Marking for tense, aspect and voice

In some languages, infinitives may be marked for grammatical categories like voice, aspect, and to some extent tense. This may be done by inflection, as with the Latin perfect and passive infinitives, or by periphrasis, as with the Latin future infinitives or the English perfect and progressive infinitives.
Latin has present, perfect and future infinitives, with active and passive forms of each. For details see.
English has infinitive constructions that are marked for aspect: perfect, progressive, or a combination of the two. These can also be marked for passive voice :

eat
be eaten
have eaten
have been eaten
be eating
be being eaten
have been eating
have been being eaten

Further constructions can be made with other auxiliary-like expressions, like be going to eat or be about to eat, which have future meaning. For more examples of the above types of construction, see.
Perfect infinitives are also found in other European languages that have perfect forms with auxiliaries similarly to English. For example, avoir mangé means in French.

English

The term infinitive is traditionally applied to the unmarked form of the verb when it forms a non-finite verb, whether or not introduced by the particle to. Hence sit and to sit, as used in the following sentences, would each be considered an infinitive:

I can sit here all day.
I want to sit on the other chair.

The form without to is called the bare infinitive; the form introduced by to is called the full infinitive or to-infinitive.
The other non-finite verb forms in English are the gerund or present participle, and the past participle – these are not considered infinitives. Moreover, the unmarked form of the verb is not considered an infinitive when it forms a finite verb: like a present indicative, subjunctive, or imperative.
Certain auxiliary verbs are modal verbs are complemented by a bare infinitive verb. periphrastic items, such as had better or ought to as substitutes for should, used to as a substitute for did, and be able to for can, are similarly complemented by a bare infinitive verb. Infinitives are negated by simply preceding them with not. Of course the verb do, when complementing a finite verb, occurs as an infinitive. However, the auxiliary verbs have and be often occur as an infinitive: "I should have finished by now"; "It's thought to have been a burial site"; "Let him be released"; "I hope to be working tomorrow."
Huddleston and Pullum's Cambridge Grammar of the English Language does not use the notion of the "infinitive", only that of the infinitival clause, noting that English uses the same form of the verb, the plain form, in infinitival clauses that it uses in imperative and present-subjunctive clauses.
A matter of controversy among prescriptive grammarians and style writers has been the appropriateness of separating the two words of the to-infinitive. For details of this, see split infinitive. Opposing linguistic theories typically do not consider the to-infinitive a distinct constituent, instead regarding the scope of the particle to as an entire verb phrase; thus, to buy a car is parsed like to .

Uses of the infinitive

The bare infinitive and the to-infinitive have a variety of uses in English. The two forms are mostly in complementary distribution – certain contexts call for one, and certain contexts for the other; they are not normally interchangeable, except in occasional instances like after the verb help, where either can be used.
The main uses of infinitives are varied:

Complementing the dummy auxiliary do, e.g., "I do like coffee but I don't care for tea."
In a bare infinitive form as an object complement, i.e.
As a bare infinitive that comprises a phrase rendered in the vestigial permissive mood, e.g. "Let it be."
As a bare infinitive that comprises a phrase rendered as a hortative utterance, e.g. "Let's leave."
As complements of certain fossil phrases such as had better and would rather, in order to, as if to, am to/is to/are to.
As a noun phrase, expressing its action or state in an abstract, general way that functions, e.g. as
Adverbially:
Adjectivally, characterizing a noun, e.g. "a request to see someone" or "the method to use."
In elliptical questions : "I don't know where to go."
In sentence fragment that constitutes an interrogative

The infinitive typically is the dictionary form or citation form of a verb. The form listed in a dictionary entry is the bare infinitive, but the to-infinitive is often used when defining other verbs, e.g.
For further detail and examples of the uses of infinitives in English, see Bare infinitive and To-infinitive in the article on uses of English verb forms.

Other Germanic languages

The original Proto-Germanic ending of the infinitive was -an, with verbs derived from other words ending in -jan or -janan.
In German it is -en, with -eln or -ern endings on a few words based on -l or -r roots. The use of zu with infinitives is similar to English to, but is less frequent than in English. German infinitives can form nouns, often expressing abstractions of the action, in which case they are of neuter gender: das Essen means, but also.
In Dutch infinitives also end in -en, sometimes used with te similar to English to, e.g., "Het is niet moeilijk te begrijpen" →. The few verbs with stems ending in -a have infinitives in -n. Afrikaans has lost the distinction between the infinitive and present forms of verbs, with the exception of the verbs wees, which admits the present form is, and the verb hê, whose present form is het.
In North Germanic languages the final -n was lost from the infinitive as early as 500–540 AD, reducing the suffix to -a. Later it has been further reduced to -e in Danish and some Norwegian dialects. In the majority of Eastern Norwegian dialects and a few bordering Western Swedish dialects the reduction to -e was only partial, leaving some infinitives in -a and others in -e. In northern parts of Norway the infinitive suffix is completely lost or only the -a is kept. The infinitives of these languages are inflected for passive voice through the addition of -s or -st to the active form. This suffix appeared in Old Norse as a contraction of mik or sik and originally expressed reflexive actions: kallar + -sik > kallask. The suffixes -mk and -sk later merged into -s, which evolved to -st in the western dialects. The loss or reduction of -a in the active voice in Norwegian did not occur in the passive forms, except for some dialects that have -es. The other North Germanic languages have the same vowel in both forms.