Imperfective

In Russian and some other languages in the group, perfective verbs have past and future tenses, while imperfective verbs have past, present and future, the imperfective future being a compound tense in most cases.

Most Bulgarian verbs can be grouped in perfective-imperfective pairs (imperfective/perfective: идвам/дойда "come", пристигам/пристигна “arrive”).

Tenses of the imperfective aspect The tenses of the imperfective aspect are present, imperfect, and future tense.

Although languages that are described as having imperfective and perfective aspects agree in most cases in their use of these aspects, they may not agree in every situation.

Although the verbs' meaning is similar, in perfective verbs the action is completed and in imperfective verbs it is ongoing.

Classical Irish had a three-way aspectual contrast of simple–perfective–imperfective in the past and present tenses.

Common aspectual distinctions The most fundamental aspectual distinction, represented in many languages, is between perfective aspect and imperfective aspect.

Consequently each language contains many pairs of verbs, corresponding to each other in meaning, except that one expresses perfective aspect and the other imperfective.

Conversely, verbs describing immediate states of change—for example, otěhotnět (to become pregnant) and nadchnout se (to become enthusiastic)—have no imperfective aspect.

Explicit consideration of aspect as a category first arose out of study of the Slavic languages ; here verbs often occur in the language in pairs, with two related verbs being used respectively for imperfective and perfective meanings.

In addition to that, past compound forms using participles vary in gender (masculine, feminine, neuter) and voice (active and passive) as well as aspect (perfective/aorist and imperfective).

Most verbs are part of inflected aspect pairs—for example, koupit (perfective) and kupovat (imperfective).

Most verbs come in pairs, with the perfective verb being created out of the imperfective by adding a prefix or making a stem change.

Normally, in grammar books these formations are viewed as separate tenses – i. e. "past imperfect" would mean that the verb is in past tense, in the imperfective aspect, and in the indicative mood (since no other mood is shown).

Perfective verbs can be usually formed from imperfective ones by suffixation or prefixation, but the resultant verb often deviates in meaning from the original.

Romance languages Modern Romance languages merge the concepts of aspect and tense but consistently distinguish perfective and imperfective aspects in the past tense.

Slavic languages main The Slavic languages make a clear distinction between perfective and imperfective aspects; it was in relation to these languages that the modern concept of aspect originally developed.

The aorist was the "simple past", while the imperfective denoted uncompleted action in the past, and the perfect was used for past events having relevance to the present.

The difference between the present indicative and the present subjunctive tense is that the subjunctive can be formed by both perfective and imperfective verbs.

The four perfect constructions above can vary in aspect depending on the aspect of the main-verb participle; they are in fact pairs of imperfective and perfective aspects.