In grammar, the perfective aspect is an aspect that exists in many languages. For reasons outlined in Grammatical aspect#Confusing terminology: perfective vs. perfect, the term "perfective aspect" is variously taken to refer to one of two quite different concepts. More commonly, nowadays, it refers to an action viewed as a single whole, and it is equivalent to the aspectual component of tenses variously called "aorist", "preterite", "simple past" and the like. In some usages, however, it can mean the same thing as the perfect aspect, which refers to a state resulting from a previous action (also described as a previous action with relevance to a particular time, or a previous action viewed from the perspective of a later time). The rest of this article assumes the first definition. Grammar is the study of rules governing the use of language. ... To meet Wikipedias quality standards, this article may require cleanup. ... To meet Wikipedias quality standards, this article may require cleanup. ... Aorist (from Greek αοριστος, indefinite) is a term used in certain Indo-European languages to refer to a particular grammatical tense and/or aspect. ... This article is about the grammatical term. ... This article is about the grammatical term. ... The perfect aspect is a grammatical aspect, which refers to a state resulting from a previous action (also described as a previous action with relevance to a particular time, or a previous action viewed from the perspective of a later time). ...

The perfective aspect, referring to a single event conceived as a unit, is distinguished from the imperfective aspect, which represents an event in the process of unfolding, or a repeated or habitual event and from the prospective aspect, representing an event that is 'about to' take place. In the past tense, it is often translated in English by the simple past form "X-ed", as compared to the imperfective, which is translated as the progressive "was X-ing". For example, the perfective would translate both verbs in the sentence "He raised his sword and struck the enemy". However, in the sentence "As he was striking the enemy, he was killed by an arrow", the first verb would be rendered by an imperfective and the second by a perfective. The imperfective aspect, sometimes known as the continuous or progressive aspect, is a grammatical aspect. ...

There are a number of important qualifications, however:

• Verbs that represent ongoing states, rather than actions, are usually rendered in English with the simple past, but would be rendered with the imperfective and not the perfective, for example, "He had two dogs" or "There was a chair on the floor".
• The English simple past can be used to represent habitual actions, which would also be rendered as an imperfective, such as "He walked his dog every day".
• Although the perfective is often described as corresponding to a "momentary action", it can equally well be used for an action that took time, as long as it is conceived of as a unit, with a clearly defined start and end, such as "Last summer I visited France".
• For some verbs in some languages, the difference between perfective and imperfective conveys an additional meaning difference; in such cases, the two aspects will typically be translated using separate verbs in English. In Greek, for example, the imperfective sometimes adds the notion of "try to do something" (the so-called conative imperfect); hence the same verb, in the imperfective (present or imperfect tense) and aorist, respectively, is used to convey look and see, search and find, listen and hear. (For example, ηκουομεν ēkouomen "we listened" vs. ηκουσαμεν ēkousamen "we heard".) Spanish has similar pairs for certain verbs, such as (imperfect and preterite, respectively) sabía "I knew" vs. supe "I found out", podía "I was able to" vs. pude "I succeeded (in doing something)", quería "I wanted to" vs. quise "I tried to", no quería "I didn't want to" vs. no quise "I refused (to do something)". Such differences are often highly language-specific.