Тіл біліміндегі белгісіз етістіктер (Тіл біліміндегі агент емес этистіктер)

In linguistics, an unaccusative verb is an intransitive verb whose grammatical subject is not a semantic agent. In other words, the subject does not actively initiate, or is not actively responsible for, the action expressed by the verb. An unaccusative verb's subject is semantically similar to the direct object of a transitive verb or to the subject of a verb in the passive voice. Examples in English are "the tree fell"; "the window broke". In those sentences, the action (falling, breaking) can be considered as something that happened to the subject, rather than being initiated by it. Semantically, the word "tree" in the sentence "the tree fell" plays a similar role as it does in a transitive sentence, such as "they cut down the tree", or its passive transformation "the tree was cut down". Unaccusative verbs thus contrast with unergative verbs, such as run or resign, which describe actions voluntarily initiated by the subject. They are called unaccusative because although the subject has the semantic role of a patient, it is not assigned accusative case. In nominative–accusative languages, the accusative case, which marks the direct object of transitive verbs, usually represents the non volitional argument (often the patient). However, for unaccusative verbs, although the subject is non volitional, it is not marked by the accusative. As Perlmutter points out, the same verb such as "slide" can be either unaccusative or unergative, depending on whether the action was involuntary or voluntary. The term "unaccusative verb" was first used in a 1978 paper by David M. Perlmutter of the University of California, San Diego. Perlmutter credited the linguist Geoffrey K. Pullum with inventing the terms "unaccusative" and "unergative".

The derivation of the core properties of unaccusative constructions from a set of principles is one of the topmost issues of the agenda of modern syntax since the seminal work by Perlmutter 1978 (cf. Burzio 1986 and Hale Keyser 2003 for landmark proposals). Perlmutter introduced the "Unaccusative Hypothesis" in 1978 explaining that intransitive verbs are not homogeneous, but are either unaccusative verbs or unergative verbs. The Unaccusative Hypothesis was later integrated into the Government and Binding Theory by Burzio (1986). The Unaccusative Hypothesis (UH) argues that the Object of the sentence becomes the Subject in the derivation, meanwhile unergatives start as subjects. More specifically, the first approach introduced by the Unaccusative Hypothesis arrived at an important consequence constituting an analogy between English passive voice constructions and unaccusative constructions whereas in the second approach a more radical theory was proposed based on the analysis of expletive there stemming from the sentences with the copula suggested in Moro 1997.

While L2 learners have difficulties with the distinction between unaccusative and unergative verbs, children when learning their first language do not encounter those same difficulties. Studies have shown that children as young as 2 years old can distinguish between unaccusative and unergative verbs. Tests have been done on 2 year olds in Hebrew and Portuguese (Friedmann 2007), on 4 & 5 year olds in German and Dutch (van Hout, 1996; Randall, van Hout, Baayen & Weissenborn, 2004), 2 & 3 year olds in Italian and French (Lorusso, Caprin, and Guasti 2004, Snyder et al., 1995), and 3 6 year olds in Russian (using Genitive of Negation tests) (Babyonyshev et al. 2001). These studies all concluded that children from a young age are able to differentiate between unaccusatives, unergatives, and transitives.

Further linguistic studies have shown that intransitive verbs will identify as either unergative or unaccusative, determined by the language. A recent study proposed by James Baker in 2019 suggests that intransitive verbs not only identify as either unaccusative or unergative, but with multiple different classes. According to Baker, the Split Intransitivity analysis has various advantages over the traditional approach in terms of argument structure. The original traditional hypothesis proposed by Levin & Rappaport Hovav in 1995 mentions linking rules referring to either an external or internal argument. In Split Intransitivity, Baker introduces additional components to the processing of unaccusative verbs he calls Initiation, State, and Change.

The Unaccusative Trap Hypothesis, developed by Oshita in 1997 and 2001, proposes to bring several unaccusative related phenomena cross linguistically and to address L2 acquisition on unaccusative verbs. According to Oshita, L2 learners undergo a 3 step process before they have the knowledge to distinguish between unaccusative and unergative verbs. In the Unaccusative Trap Hypothesis, at the first stage, unaccusatives are acquired as unergatives in L2 learners. In the second stage, L2 learners realize and become awakened to the natural linking rules proposed by Levin and Rappaport Havov in 1995. Even in this second stage, there is a stage of syntactic confusion with derivations into the sentence structure. Since Unaccusatives have different syntactic rules for their target languages, the non target interlanguage phenomena for Japanese or other languages, for example, will be different than those observed in English. Oshita mentions that L2 learners must unlearn non target syntactic operations and reach the third stage. By this stage, they are out of confusion and can understand unaccusative constructions natively. This study, discussed by Junhua Mo in 2020, analyzed the Unaccusative Trap Hypothesis with L2 English learners and calls for further study. The linking rules associated proposed by Levin and Rappaport Hovav were only effective for L1 acquisition of English, not applicable to L2 acquisition.

According to linguistic theory, unaccusative verbs have sentences that undergo lexical and syntactic operations that do not occur with unergative and transitives. A recent study in 2010 by Friedmann, Shetreet, and Hadar explains and supports this linguistic theory by showing that there are two separate activation locations from unaccusative and unergative verbs in the brain. This study focused on neural correlations of linguistic distinction between Unaccusatives and Unergatives. This study was taken from participants who were tested in their native language, Hebrew. The differences between Unaccusative and Unergative (and transitive) verbs arose from differences in syntactic and lexical derivations.

Unaccusative and unergative verbs, while syntactically different, are communicated the same on the surface. They both include a noun phrase (NP) followed by a verb phrase (VP) when produced. In generative grammar, an unaccusative verb is analysed as having an underlying VP shell in which the NP is selected by the bottom most VP and later moved. For an unergative verb, on the other hand, the NP is selected by the topmost VP in a VP shell, and therefore is not required to move to create a surface level order of the noun being followed by the verb. The image to the right demonstrates how the noun in an unaccusative is the direct object of the sentence, as it is selected by the VP as a complement, whereas the noun in an unergative is the subject of the sentence.