In linguistics, an impersonal verb is one that has no determinate subject. For example, in the sentence "It rains", rain is an impersonal verb and the pronoun it does not refer to anything. In many languages the verb takes a third person singular inflection and often appears with an expletive subject. In the active voice, impersonal verbs can be used to express operation of nature, mental distress, and acts with no reference to the do-er. Impersonal verbs are also called weather verbs because they frequently appear in the context of weather description.
Impersonal verbs appear only as infinitives or with third-person inflection(s). In the third person, the subject is either implied or a dummy referring to people in general. The term "impersonal" simply means that the verb does not change according to grammatical person. In terms of valency, impersonal verbs are often avalent, as they often lack semantic arguments. In the sentence It rains, the pronoun it is a dummy subject; it is merely a syntactic placeholder - it has no concrete referent. In many other languages, there would be no subject at all. In Spanish, for example, It is raining could be expressed as simply llueve.
Forms of impersonal verb 
Invisible arguments 
When an agent is unspecified, impersonal verbs are also known as zero person construction, or impersonal construction. An implicit argument (an argument that is put forth without stating it directly) is present on a semantic level for both Estonian and Finnish. The Finnic impersonal construction enables an event or state to be described without specifying the identity of the agent (actor). Despite this, the interpretation of the impersonal includes a referent of some sort (dummy). The zero person is not entirely the same as an impersonal.
- Sunnuntaina voi nukkua pitkään.
- Sunday-on can.PRS.3sg sleep.INF long.
- Pühapäeviti saab sisse magada.
- on-Sundays can.PRS.3sg in.ILL sleep.INF
- On Sundays you/one can sleep in.
There is a lack of an overt nominative subject in these constructions.
Some languages require their counterpart to the English by-phrase be present (like Palauan and Indonesian, Austronesian languages). Other languages disallow the presence of a by-phrase. For example, Polish does not allow the use of a by-phrase in its passive.
- Zapukano w drzwi (*przez sasiada)
- was-knocked at door (*by neighbor)
- It was knocked at the door.
- Someone knocked at the door.
The content in the parenthesis causes the Polish sentence to be ungrammatical as who did the knocking cannot be overtly stated. As such, it might seem like it would be more grammatical to use impersonal verbs in such cases.
Impersonal verb in various languages 
In some languages such as English, French, German and Dutch, an impersonal verb always takes an impersonal pronoun (it in English, il in French, es in German, het in Dutch) as its syntactical subject:
- It snowed yesterday. (English)
- Il a neigé hier. (French)
- Il risque de pleuvoir. (Title of a novel by Emmanuelle Heidsieck)
- Es schneite gestern. (German)
- Het sneeuwde gisteren. (Dutch)
Occasionally an impersonal verb will allow an object to appear in apposition to the impersonal subject pronoun:
- It is raining diamonds.
Or as an instrumental adjunct:
- It was pouring with rain. (British English)
- Весь декабрь заливало дождём. (Russian)
In some other languages (necessarily null subject languages and typically pro-drop languages), such as Portuguese, Spanish, Occitan, Catalan, Italian, Romanian, in Hungarian and all the Slavic languages, an impersonal verb takes no subject at all, but it is conjugated in the third-person singular, which is much as though it had a third-person, singular subject.
- Nevó ayer. (Spanish)
- Nevou ontem. (Portuguese)
- Ha nevicato ieri. (Italian)
- Sniježilo je jučer. (Croatian)
- Havazott tegnap. (Hungarian)
- Вчера вееше снег. / Včera veeše sneg. (Macedonian)
Other languages, those which require a subject, may permit an adjunct to assume that role.
- Unfortunately the next day poured with rain.
In English 
The following sentences illustrate impersonal verbs:
- (1) It rains.
- (2) It is cold.
- (3) It is growing dark.
- (4) It seems that there is no end to this.
- (5) It is unclear why he cut the rope.
The expletive pronoun it in these sentences does not denote a clear entity, yet the meaning is clear. In other words, the pronoun it has no clear antecedent. English is so strict about requiring a subject that it supplies them for verbs that do not really require them. In sentences (4) and (5), it is in the subject position, while the real subject has been moved to the end of the sentence.
A simple test can be done to see if the sentence contains an impersonal verb. One checks to see if a given subject pronoun takes an antecedent in the previous clause or sentence, e.g.
- Bukit Timah is 163.63 metres tall. It is the highest point in Singapore.
- Bukit Timah is 163.63 metres tall. It rains frequently there.
The two examples may seem similar, but only the pronoun it in the first example links with the previous subject. The pronoun it in the second example, on the other hand, has no referent. The hill (Bukit Timah) does not rain, it rains. This demonstrates that rain is an impersonal verb.
In Spanish 
In Spanish, the usage of impersonal verbs stands alone, and involves using a third-person conjugation. There is no equivalent of “it” in Spanish. Sometimes known as a defective verb, impersonal verbs are conjugated in the third person only. An example of an impersonal verb usage is in the common verb es in Es verdad que estoy loco. Spanish utilizes a different format when expressing impersonal verbs in its sentences. Spanish will add the pronoun se in front of verbs to form general sentences. Impersonal voice using se will use a singular verb since se can be replaced by uno.
- ¿Cómo se escribe "Apple"?
- How do you spell “Apple”?
The passive voice in Spanish has similar characteristics following that of the impersonal se. It is normally formed by using se + the third person singular or plural conjugation of a verb, similar to the impersonal se.
- Active voice:
- Mis amigos comieron la torta
- My friends ate the cake
- Passive voice:
- Se comió la torta.
- The cake was eaten
Another common Spanish impersonal verb is: Haber (to exist). Haber is an irregular verb. It has a special conjugation for the third person when used as an impersonal verb in the present tense. When using it as an impersonal verb, it uses the conjugated form hay. Clauses with the verb haber do not have an explicit subject. This impersonal verb requires a direct object noun phrase. Haber has its 'natural meaning' of tener ‘to have’.
- Hay muchos libros.
- There are many books
In French 
The verbs are impersonal in French because they cannot take a real personal subject as they do not represent any action, occurrence or state-of-being that can be attributed to a person, place or a thing. In other words, although subject to dispute perhaps, no one In French, as in English, these impersonal verbs take on the impersonal pronoun - il in this case.
- Il faut que tu fasses tes devoirs.
- It is necessary that you do your homework.
The il does not refer to anything in particular here. They are dummy forms. The meaning is doing your homework is necessary. The most common impersonal form is il y a = there is, there are. Note its other tenses (il y avait, il y a eu, il y aura, etc.).
In Thai 
- kəət3 phɛɛndinwaày thîï4 yîïpùn
- happen earthquake at Japan
- There is an earthquake in Japan.
- *man kəət3 phɛɛndinwaày thîï4 yîïpùn
- *it happen earthquake in Japan
- *There is an earthquake in Japan.
There is no allowance for the presence of a non-referential subject man ‘it’ in the case frame. In general, this is not allowed in formal speech such as in news reports. However,the presence of non-referential subject man can occur in the colloquial form.
- man mii phîï nay bâan nii dûay rəə
- it exist ghost in house this also Ques
- Is there also a ghost in this house?
Subdivision into non-inception and inception subclasses can occur depending on whether the verb may occur with the path adverb khin ‘up’.
In other languages 
- Il ha nivate heri. (Interlingua)
In the planned auxiliary language Esperanto, where verbs also are not conjugated for person, impersonal verbs are simply stated with no subject given or implied, even though Esperanto is otherwise not a null subject language:
- Neĝis hieraŭ. (Esperanto)
The Celtic languages also possess impersonal verbal forms, though their use is usually translated into English by forms such as 'one sees' (Welsh: gwelir), 'one did' (Welsh: gwnaethpwyd), 'one is' (Irish: táthar) etc., where the 'one' is taken to be an empty subject. For weather, personal verbs are used in Celtic languages, e.g. Welsh Mae hi'n bwrw eira 'it is snowing'.
Verbs meaning existence may also be impersonal.
- Há livros. / Há um livro. (Portuguese)
- Hay libros. / Hay un libro. (Spanish)
- There are (some) books. / There is a book.
- Existem livros. / Existe um livro. (Portuguese)
- Existen libros. / Existe un libro. (Spanish)
- (Some) books exist. / A book exists.
Latin has several impersonal verbs, most often seen in the third person singular. The real subject of the sentence will not be in the nominative case, instead it is most often in the dative or accusative case. These verbs include:
- Decet - it becomes/suits; it is right/proper
- Libet - it pleases
- Licet - it is permitted/allowed
- Oportet - it is proper/fitting
- Placet - it is agreed/resolved
Comparison to other linguistic classifications 
Weather verb 
Some linguists consider the impersonal subject of a weather verb to be a "dummy pronoun", while others interpret it differently.
Adjectives of zero valence are mainly the adjectives referring to weather such as “winding” and ”raining” and so on. In some languages such as Mandarin Chinese, weather verbs like snow(s) take no subject or object.
Impersonal pronoun 
As with impersonal verbs, impersonal pronouns also functions without reference to a person in particular. In English, one can also function in an impersonal and objective manner.
- One would [You'd] think the inner dome of heaven had fallen.
- The young comedian was awful; one felt embarrassed for him.
- If one fails, then one must try harder next time.
When the pronoun one is used in the numerical sense, a different pronoun can be used subsequently to referring to the same entity.
- We watched as one [of the ospreys] dried its feathers in the sun.
- One [driver] pulled her car over to the side.
Generally, it is not ideal to mix the impersonal pronoun one with another pronoun in the same sentence.
- If one fails, then he/you must simply try harder.
Null objects 
While the concept of impersonal verbs is closely related to phenomenon of null subjects, null objects has to do with the lack of the obligatory projection of an object position.
- C'est pas lui qui l'a écrit, son livre, le pape, c'est quelqu'un qui lui écrit __....
- The Pope didn't write his book himself, someone writes __ for him.
- Why then do the psychic gifts often seem to tease__, confuse __ and obstruct__?
Null objects occur with anaphoric Direct Objects, that is, those whose referents can be understood from the prior or ongoing discourse context as well as sufficiently salience in that context to be encoded pronominally. However, it is not imperative that the Direct Object referent must have been previously referred to linguistically in the discourse; it could instead be accessible due to its perceptual salience to the interlocutors extra-linguistically during communication.
Defective verb 
An impersonal verb is different from a defective verb in that with an impersonal verb, only one possible syntactical subject is meaningful (either expressed or not), whereas with a defective verb, certain choices of subject might not be grammatically possible, because the verb does not have a complete conjugation.
Evidence for Universal Grammar 
Impersonal verbs can be considered null subject data. It involves a general concern in generative grammar: determining the nature and distribution of phonetically null but syntactically present entities (Empty Categories). Since, by definition, these entities are absent from the speech signal, it is of interest that language learners still can come to have information about them. As this phenomenon could not have resulted from sufficient prior experience, it suggests the role of Universal Grammar.
See also 
- Loureiro-Porto, L. (2010). A Review of Early English Impersonals: Evidence from Necessity Verbs. English Studies, 91(6), 674-699.
- tex's French grammar. Retrieved on 12 March 2012.
- Blevins, J. P. (2003). Passives and impersonals. Journal Of Linguistics, 39(3), 473-520.
- Kaiser, Elsi and Vihman Virve-A (2006). In Benjamin Lyngfelt, Torgrim Solsted. Demoting the Agent. Passive, middle and other voice phenomena (96 ed.). John Benjamins Publishing Company.
- Napoli, Donna Jo (1993). Syntax Theory and Problems. New York: Oxford University Press.
- Impersonal Verbs. Retrieved on 12 March 2012.
- What is an impersonal verb. Retrieved on 12 March 2012.
- Gerald Erichsen.(2012).Defective Verbs: Some Verbs Infrequently Used in All Conjugations.Retrieved on 12 March 2012.
- Deborah R. Lemon.(1994). The Impersonal and Passive se in Spanish. Retrieved on 12 March 2012.)
- Kany, Charles. 1945. American-Spanish syntax. Chicago: The University of Chicago Press.
- Transparent Language. (2008). Impersonal Verbs. Retrieved on 12 March 2012.
- Impersonal verbs. Retrieved on 12 March 2012.
- Indrambarya, Kitima (1996). On Impersonal Verbs in Thai. Text "Department of Foreign Languages Kasetsart University" ignored (help)
- A Complete Grammar of Esperanto
- Huang Jinzhu & Mianzhu Yi (2010) ,The design and implementation of VDEA Universal Communication Symposium (IUCS), 2010 4th International , 325-331
- Ask Define. Retrieved on 20 March 2012.
- On the Uses of One. Retrieved on 20 March 2012.
- Cummins S., Roberge, Y., (2004). Null objects in French and English. In: Auger, J., Clements, J.C., Vance, B. (Eds.), Contemporary Approaches to Romance Linguistics: Selected papers from the 33rd Linguistic Symposium on Romance Languages (LSRL). John Benjamins, Amsterdam, 121–138.
- Schwenter, Scott A (2006). Null Objects across South America. Selected Proceedings of the 8th Hispanic Linguistics Symposium, ed. Timothy L. Face and Carol A. Klee, 23-36. Somerville, MA: Cascadilla Proceedings Project.
- Jaeggli, Osvaldo and Safir, Kenneth J. (1989). The Null Subject Parameter and Parametric Theory. The Netherlands: Kluwer Academic Publishers.