The imperfective (abbreviated NPFV, IPFV, or more ambiguously IMPV) is a grammatical aspect used to describe ongoing, habitual, repeated, or similar semantic roles, whether that situation occurs in the past, present, or future. Although many languages have a general imperfective, others have distinct aspects for one or more of its various roles, such as progressive, habitual, and iterative aspects. The imperfective contrasts with the perfective aspect, which is used to describe actions viewed as a complete whole.

English is an example of a language with no general imperfective. The English progressive is used to describe ongoing events, but can still be used in past tense, such as "The rain was beating down". Habitual situations do not have their own verb form (in most dialects), but the construction "used to" conveys past habitual action, as in I used to ski. Unlike in languages with a general imperfective, in English the simple past tense can be used for situations presented as ongoing, such as The rain beat down continuously through the night.

A contrast between the progressive and imperfective is seen with stative verbs. In English, stative verbs, such as know, do not use the progressive (*I was knowing French is ungrammatical), while in languages with an imperfective (for instance, French), stative verbs frequently appear in the imperfective.

Verbs in Hindi-Urdu (Hindustani) have their grammatical aspects overtly marked. Periphrastic Hindi-Urdu verb forms (participle verb forms) consist of two elements, the first of these two elements is the aspect marker and the second element (the copula) is the common tense-mood marker. There are two independent imperfective aspects in Hindi-Urdu: Habitual Aspect, and Progressive Aspect. These two aspects are formed from their participle forms being used with the copula verb of Hindi which is होना honā (to be). However, the aspectual participles can also have the verbs रहना rêhnā (to stay/remain), आना ānā (to come) & जाना jānā (to go) as their copula. The table below shows three verbs होना honā (to be), करना karnā (to do), and मरना marnā (to die) in their aspectual infinitive forms using different copulas.

Some translations are approximate, and the nuance cannot be expressed exactly in English. Some aspectual forms also have the same translations in English but are not interchangeable in Hindi-Urdu.

Now, these copula verbs (besides होना honā) can themselves be converted into their participle forms and put into one of the three different aspects of Hindi-Urdu, which are habitual, progressive, and perfective aspects, hence generating sub-aspectual infinitive forms. This way a verb form combining two grammatical aspects is constructed. The table below shows the combined aspectual forms:

The perfective subaspect of the habitual main aspect (habitual) also is imperfective (habitual). Also, these sub-aspects are even more nuanced that it is not possible to translate each of them into English in a unique way. Some translations don't even make sense in English.

Verbs in Slavic languages have a perfective and/or an imperfective form. Generally, any of various prefixes can turn imperfectives into perfectives; suffixes can turn perfectives into imperfectives. The non-past imperfective form is used for the present, while its perfective counterpart is used for the future. There is also a periphrastic imperfective future construction.