In linguistics, the grammatical aspect of a verb is a grammatical category that defines the temporal flow (or lack thereof) in a given action, event, or state, from the point of view of the speaker. A basic distinction is with regard to whether the speaker looks at a situation as bounded and unitary, without reference to any flow of time during the situation ("I ate"), or with no reference to temporal bounds but with reference to the nature of the flow of time during the situation ("I was eating", "I used to eat"). The unitary view without internal temporal flow is known as the perfective aspect, while the non-bounded view with reference to temporal flow is known as the imperfective aspect. Within the imperfective aspect, further common aspectual distinctions include whether the situation is repetitive or habitual ("I used to eat"), is continuous in a particular time frame ("I was eating"), or has continuing relevance in a later time frame ("I have eaten"). Any one language has only a subset of the aspectual distinctions attested in the world's languages, and some languages (such as Standard German; see below) do not have aspects.
Grammatical aspect may have been dealt with for the first time in the work of the Indian linguist Yaska (ca. 7th century BCE), who distinguished actions that are processes (bhāva), from those where the action is considered as a completed whole (mūrta). This is the key distinction between the imperfective and perfective. Yaska also applied this distinction to a verb versus an action nominal.
Greek and Latin grammarians were also interested in aspect, but the idea did not enter into the modern Western grammatical tradition until the nineteenth century, via the study of Slavic grammar. English usage of the term dates from 1853, when it first appeared in the Oxford English Dictionary.
Aspect is often confused with the closely related concept of tense, because they both convey information about time. While tense relates the time of a situation to some other time, commonly the time of speaking, aspect conveys other temporal information, such as duration, completion, or frequency, as it relates to the time of action. Thus tense refers to temporally when while aspect refers to temporally how. Aspect can be said to describe the texture of the time in which a situation occurs, such as a single point of time, a continuous range of time, a sequence of discrete points in time, etc., whereas tense indicates its location in time.
For example, consider the following sentences: "I eat", "I am eating", "I have eaten", and "I have been eating". All are in the present tense, as they describe the present situation, yet each conveys different information or points of view as to how the action pertains to the present. As such, they differ in aspect.
Grammatical aspect is a formal property of a language, distinguished through overt inflection, derivational affixes, or independent words that serve as grammatically required markers of those aspects. For example, the K'iche' language spoken in Guatemala has the inflectional prefixes k- and x- to mark incompletive and completive aspect;  Mandarin Chinese has the aspect markers -le, -zhe, zài-, and -guo to mark the perfective, durative stative, durative progressive, and experiential aspects, and also marks aspect with adverbs; and English marks the continuous aspect with the verb to be coupled with present participle and the perfect with the verb to have coupled with past participle. Even languages that do not mark aspect morphologically or through auxiliary verbs, however, can convey such distinctions by the use of adverbs or other syntactic constructions.
Grammatical aspect is distinguished from lexical aspect or aktionsart, which is an inherent feature of verbs or verb phrases and is determined by the nature of the situation that the verb describes.
The most fundamental aspectual distinction, represented in many languages, is between perfective aspect and imperfective aspect. This is the basic aspectual distinction in the Slavic languages. It semantically corresponds to the distinction between the morphological forms known respectively as the aorist and imperfect in Greek, the preterite and imperfect in Spanish, the simple past (passé simple) and imperfect in French, and the perfect and imperfect in Latin (from the Latin "perfectus", meaning "completed").
Essentially, the perfective aspect looks at an event as a complete action, while the imperfective aspect views an event as the process of unfolding or a repeated or habitual event (thus corresponding to the progressive/continuous aspect for events of short-term duration and to habitual aspect for longer terms). For events of short durations in the past, the distinction often coincides with the distinction in the English language between the simple past "X-ed," as compared to the progressive "was X-ing" (compare "I wrote the letters this morning" (i.e. finished writing the letters: an action completed) and "I was writing letters this morning"). In describing longer time periods, English needs context to maintain the distinction between the habitual ("I called him often in the past" - a habit that has no point of completion) and perfective ("I called him once" - an action completed), although the construct "used to" marks both habitual aspect and past tense and can be used if the aspectual distinction otherwise is not clear.
Sometimes, English has a lexical distinction where other languages may use the distinction in grammatical aspect. For example, the English verbs "to know" (the state of knowing) and "to find out" (knowing viewed as a "completed action") correspond to the imperfect and perfect of the French verb "savoir".
Aspect is a somewhat difficult concept to grasp for the speakers of most modern Germanic languages, because they tend to conflate the concept of grammatical aspect with that of tense. Although English largely separates tense and aspect formally, its generally recognized aspects do not correspond very closely to the traditional notion of perfective vs. imperfective aspectual distinction originally devised to classify aspect in most Classical and Slavic languages (those languages for which the concept of aspect was first proposed in describing non-tense handling of verbal "viewpoint").
Like tense, aspect is a way that verbs represent time. However, rather than locating an event or state in time, the way tense does, aspect describes "the internal temporal constituency of a situation", or in other words, aspect is a way "of conceiving the flow of the process itself". English aspectual distinctions in the past tense include "I went, I used to go, I was going, I had gone"; in the present tense "I lose, I am losing, I have lost, I have been losing, I am going to lose"; and with the future modal "I will see, I will be seeing, I will have seen, I am going to see". What distinguishes these aspects within each tense is not (necessarily) when the event occurs, but how the time in which it occurs is viewed: as complete, ongoing, consequential, planned, etc.
In most dialects of Ancient Greek, aspect is indicated uniquely by verbal morphology. For example, the very frequently used aorist, though a functional preterite in the indicative mood, conveys historic or 'immediate' aspect in the subjunctive and optative. The perfect in all moods is used as an aspectual marker, conveying the sense of a resultant state. E.g. Greek, Ancient (to 1453): ὁράω - I see (present); Greek, Ancient (to 1453): εἶδον - I saw (aorist); Greek, Ancient (to 1453): οἶδα - I am in a state of having seen = I know (perfect).
Many Sino-Tibetan languages, like Mandarin, lack grammatical tense but are rich in aspect.
See main article: Lexical aspect. There is a distinction between grammatical aspect, as described here, and lexical aspect. Lexical aspect is an inherent property of a verb or verb-complement phrase, and is not marked formally. The distinctions made as part of lexical aspect are different from those of grammatical aspect. Typical distinctions are between states ("I owned"), activities ("I shopped"), accomplishments ("I painted a picture"), achievements ("I bought"), and punctual, or semelfactive, events ("I sneezed"). These distinctions are often relevant syntactically. For example, states and activities, but not usually achievements, can be used in English with a prepositional for-phrase describing a time duration: "I had a car for five hours", "I shopped for five hours", but not "*I bought a car for five hours". Lexical aspect is sometimes called Aktionsart, especially by German and Slavic linguists. Lexical or situation aspect is marked in Athabaskan languages.
One of the factors in situation aspect is telicity. Telicity might be considered a kind of lexical aspect, except that it is typically not a property of a verb in isolation, but rather a property of an entire verb phrase. Achievements, accomplishments and semelfactives have telic situation aspect, while states and activities have atelic situation aspect.
The other factor in situation aspect is duration, which is also a property of a verb phrase. Accomplishments, states, and activities have duration, while achievements and semelfactives do not.
In some languages, aspect and time are very clearly separated, making them much more distinct to their speakers. There are a number of languages that mark aspect much more saliently than time. Prominent in this category are Chinese and American Sign Language, which both differentiate many aspects but rely exclusively on optional time-indicating terms to pinpoint an action with respect to time. In other language groups, for example in most modern Indo-European languages (except Slavic languages), aspect has become almost entirely conflated, in the verbal morphological system, with time.
In Russian, aspect is more salient than tense in narrative. Russian, like other Slavic languages, uses different lexical entries for the different aspects, whereas other languages mark them morphologically, and still others with auxiliaries (e.g., English).
In literary Arabic (الفصحى, al-Fusha) the verb has two aspect-tenses: perfective (past), and imperfective (non-past). There is some disagreement among grammarians whether to view the distinction as a distinction in aspect, or tense, or both. The "Past Verb" (فعل ماضي, fi'l maadiy) denotes an event (حدث, hadath) completed in the past, but says nothing about the relation of this past event to present status. For example, "وصل", wasala, "he arrived", indicates that arrival occurred in the past without saying anything about the present status of the arriver - maybe he stuck around, maybe he turned around and left, etc. - nor about the aspect of the past event except insofar as completeness can be considered aspectual. This "Past Verb" is clearly similar if not identical to the Greek Aorist, which is considered a tense but is more of an aspect marker. In the Arabic, aorist aspect is the logical consequence of past tense. By contrast, the "Verb of Similarity" (فعل المضارع, fi'l al-mudaara'ah), so called because of its resemblance to the active participial noun, is considered to denote an event in the present or future without committing to a specific aspectual sense beyond the incompleteness implied by the tense: يضرب "yadribu", he strikes/is striking/will strike/etc. Those are the only two "tenses" in Arabic (not counting "أمر"، "amr", command, which the tradition counts as denoting future events.) At least that's the way the tradition sees it. To explicitly mark aspect, Arabic uses a variety of lexical and syntactic devices.
Contemporary Arabic dialects are another matter. One major change from al-Fusha is the use of a prefix particle (ب "bi" in most dialects) to explicitly mark progressive, continuous, or habitual aspect: بيكتب, bi-yiktib, he is now writing, writes all the time, etc.
Aspect can mark the stage of an action. The prospective aspect is a combination of tense and aspect that indicates the action is in preparation to take place. The inceptive aspect identifies the beginning stage of an action (e.g. Esperanto uses ek-, e.g. Mi ekmanĝas, "I am beginning to eat.") and inchoative and ingressive aspects identify a change of state (The flowers started blooming) or the start of an action (He started running). Aspects of stage continue through progressive, pausative, resumptive, cessive, and terminative.
The English tense–aspect system has two morphologically distinct tenses, present and past. No marker of a future tense exists on the verb in English; the futurity of an event may be expressed through the use of the auxiliary verbs "will" and "shall", by a present form, as in "tomorrow we go to Newark", or by some other means. Past is distinguished from present-future, in contrast, with internal modifications of the verb. These two tenses may be modified further for progressive aspect (also called continuous aspect), for the perfect, or for both. These two aspectual forms are also referred to as BE +ING and HAVE +EN, respectively, which avoids what may be unfamiliar terminology.
Aspects of the present tense:
Aspects of the past tense:
(While many elementary discussions of English grammar classify the present perfect as a past tense, it relates the action to the present time. One cannot say of someone now deceased that he "has eaten" or "has been eating"; the present auxiliary implies that he is in some way present (alive), even if the action denoted is completed (perfect) or partially completed (progressive perfect).)
The uses of the progressive and perfect aspects are quite complex. They may refer to the viewpoint of the speaker:
I was walking down the road when I met Michael Jackson's lawyer. (Speaker viewpoint in middle of action)
I have traveled widely, but I have never been to Moscow. (Speaker viewpoint at end of action)
But they can have other illocutionary forces or additional modal components:
You are being stupid now. (You are doing it deliberately)
You are not having chocolate with your sausages! (I forbid it)
I am having lunch with Mike tomorrow. (It is decided)
English expresses some other aspectual distinctions with other constructions. Used to + VERB is a past habitual, as in "I used to go to school", and going to / gonna + VERB is a prospective, a future situation highlighting current intention or expectation, as in "I'm gonna go to school next year".
Note that the aspectual systems of certain dialects of English, such as African-American Vernacular English (see for example habitual be), and of creoles based on English vocabulary, such as Hawaiian Creole English, are quite different from those of standard English, and often distinguish aspect at the expense of tense.
Although Standard German does not have aspects, many Upper German languages, all West Central German languages, and some more vernacular German languages do make one aspectual distinction, and so do the colloquial languages of many regions, the so called German regiolects. While officially discouraged in schools and seen as 'bad language', local English teachers like the distinction, because it corresponds well with the English continuous form. It is formed by the conjugated auxiliary verb "sein" (to be) followed by the preposition "am" and the infinitive, or the nominalized verb. The latter two are phonetically indistinguishable; in writing, capitalization differs: "Ich war am essen" vs. "Ich war am Essen" (I was eating, compared to the Standard German approximation: "Ich war beim Essen"); yet these forms are not standardized and thus are relatively infrequently written down or printed, even in quotations or direct speech. If written, the first form (the infinitive) is preferred.
See main article: Grammatical aspect in Slavic languages.
Modern Romance languages merge the concepts of aspect and tense, but consistently distinguish perfective and imperfective aspects in the past tense. This derives directly from the way the Latin language used to render both aspects and consecutio temporum.
Italian language example (verb mangiare, to eat):
Mood: indicativo (indicative)
The imperfetto/trapassato prossimo contrasts with the passato remoto/trapassato remoto in that imperfetto renders an imperfective (continuous) past while passato remoto expresses an aorist (punctual/historical) past.
Other aspects in Italian are rendered with other periphrases, like prospective (io sto per mangiare "I'm about to eat", io starò per mangiare "I shall be about to eat"), or continuous/progressive (io sto mangiando "I'm eating", io starò mangiando "I shall be eating").
Finnish and Estonian, among others, have a grammatical aspect contrast of telicity between telic and atelic. Telic sentences signal that the intended goal of an action is achieved. Atelic sentences do not signal whether any such goal has been achieved. The aspect is indicated by the case of the object: accusative is telic and partitive is atelic. For example, the (implicit) purpose of shooting is to kill, such that:
Sometimes, corresponding telic and atelic forms have as little to do with each other semantically as "take" has with "take off". For example, naida means "to marry" when telic, but "to have sex with" when atelic.
Also, derivational suffixes exist for various aspects. Examples:
Like many Austronesian languages, the verbs of the Philippine languages follow a complex system of affixes in order to express subtle changes in meaning. However, the verbs in this family of languages are conjugated to express the aspects and not the tenses. Though many of the Philippine languages do not have a fully codified grammar, most of them follow the verb aspects that are demonstrated by Filipino or Tagalog.
Creole languages, typically use the unmarked verb for timeless habitual aspect, or for stative aspect, or for perfective aspect in the past. Invariant pre-verbal markers are often used. Non-stative verbs typically can optionally be marked for the progressive, habitual, completive, or irrealis aspect. The progressive in English-based Atlantic Creoles often uses de (from English "be"). Jamaican Creole uses pan (from English "upon") for the present progressive and wa (from English "was") for the past progressive. Haitian Creole uses the progressive marker ap. Some Atlantic Creoles use one marker for both the habitual and progressive aspects. In Tok Pisin, the optional progressive marker follows the verb. Completive markers tend to come from superstrate words like "done" or "finish", and some creoles model the future/irrealis marker on the superstrate word for "go".
American Sign Language (ASL) is similar to many other sign languages in that it has no grammatical tense but many verbal aspects produced by modifying the base verb sign.
An example is illustrated with the verb TELL. The basic form of this sign is produced with the initial posture of the index finger on the chin, followed by a movement of the hand and finger tip toward the indirect object (the recipient of the telling). Inflected into the unrealized inceptive aspect ('to be just about to tell'), the sign begins with the hand moving from in front of the trunk in an arc to the initial posture of the base sign (i.e. index finger touching the chin) while inhaling through the mouth, dropping of the jaw, directing eye gaze toward the verb's object. The posture is then held rather than moved toward the indirect object. During the hold, the signer also stops the breath by closing the glottis. Other verbs (such as 'look at', 'wash the dishes', 'yell', 'flirt') are inflected into the unrealized inceptive aspect similarly: the hands used in the base sign move in an arc from in front of the trunk to the initial posture of the underlying verb sign while inhaling, dropping the jaw, and directing eye gaze toward the verb's object (if any), but subsequent movements and postures are dropped as the posture and breath are held.
Other aspects in ASL include the following: stative, inchoative ("to begin to..."), predisposional ("to tend to..."), susceptative ("to... easily"), frequentative ("to... often"), protractive ("to... continuously"), incessant ("to... incessantly"), durative ("to... for a long time"), iterative ("to... over and over again"), intensive ("to... very much"), resultative ("to... completely"), approximative ("to... somewhat"), semblitive ("to appear to..."), increasing ("to... more and more"). Some aspects combine with others to create yet finer distinctions.
Aspect is unusual in ASL in that transitive verbs derived for aspect lose their grammatical transitivity. They remain semantically transitive, typically assuming an object made prominent using a topic marker or mentioned in a previous sentence. See Syntax in ASL for details.
The following aspectual terms are found in the literature. Approximate English equivalents are given.