All Slavic languages distinguish between at least two kinds of grammatical aspect: the imperfective aspect and the perfective aspect. While usage varies between languages, imperfective forms are typically used to signify incomplete actions, actions which occur regularly, or actions still in progress. By contrast, the perfective is commonly used to express completeness or totality, and often contextualizes an action within a specific point in time and space. The use of one aspect over another in certain contexts can connote a certain level of politeness. Aspectual pairs are typically formed using imperfectivizing suffixes or perfectivizing prefixes, though alternations in vowel quality, vowel length, or stress may also be used. Some verbs, especially loanwords, may perform the grammatical role of both aspects, though some languages deal with the ambiguity by applying a perfectivizing prefix or an imperfectivizing suffix to the word in order to give it a clearer grammatical role in the sentence.
The development of the Slavic aspectual system dates back to Proto-Slavic, the most recent common ancestor of the Slavic languages, during which aspect overtook grammatical tense's importance in verbal constructions. Although the ancestral Proto-Indo-European language also marked for aspect, it has a much more robust and central role in the Slavic languages. Over time, a system of affixation mostly replaced the inherited Proto-Indo-European system, though features persist mainly in some South Slavic languages. The exact origin of the affixation system is the subject of scholarly debate, but it appears that a major development was the semantic bleaching of certain spacial prefixes. These prefixes once had a strict semantic role, usually signifying some sort of spacial relationship such as "away from" or "with", but overuse in certain contexts caused the prefixes to be reanalyzed as serving a grammatical rather than semantic function.
Although derived from a common system, usage of aspect among the Slavic languages varies considerably. Linguists have categorized usage using an East–West isogloss to distinguish them, though the system is not based on any phylogenetic relationship; in other words, the division among these languages is not based on an internal subfamilial relationship, but similar developments which evolved in parallel. The East Slavic languages and Bulgarian comprise the Eastern group, while Czech, Slovak, Slovene, and the Sorbian languages make up the Western group. Both Polish and Serbo-Croatian defy strict categorization into either group and are treated as transitional varieties, though Polish leans east in its usage and Serbo-Croatian leans westward. Macedonian occupies a unique position, either as a particularly divergent form of the Eastern group or as a transitional language which leans further eastward than Polish.
Context Slavic languages
The Slavic languages, sometimes known as the Slavonic languages, are a subfamily of the larger Indo-European language family. Collectively, they are most closely related to the Baltic languages, best known among them being Lithuanian and Latvian. The Slavic languages descend from a common ancestral language known as Proto-Slavic. This ancestor experienced internal linguistic fragmentation during the early centuries AD and is generally considered to have diverged around 800 AD when the dialects were no longer fully mutually intelligible with one another, though the languages still retain a level of mutual intelligibility even today.
Within the larger Slavic language family, there are three major subdivisions: East Slavic, West Slavic, and South Slavic. East Slavic makes up the vast majority of speakers and includes Russian, Ukrainian, and Belarusian. The West Slavic branch is composed of languages such as Polish, Czech, and Slovak. South Slavic, the smallest group, comprises Serbo-Croatian – including its localized national varieties of Bosnian, Croatian, Serbian, and Montenegrin – as well as Bulgarian, Macedonian, and Slovene. The historical Old Church Slavonic is also a part of the South Slavic subfamily; it remains in use as a liturgical language in some varieties of Eastern Christian worship, mostly through the various Eastern Orthodox churches.
Grammatical aspect
Grammatical aspect expresses the internal, temporal structure of a verb. It contrasts with grammatical tense which only expresses the time in which an event took place relative to a deictic center, typically centered around the speech act. All Slavic languages distinguish between grammatical aspects. The term first appeared in English around 1853 to describe the function in the Slavic languages as distinct from other Western studies of grammar. The term itself is a calque, or loan translation, from the Russian word (; 'grammatical aspect', also 'sight, view').
General characteristics All Slavic languages distinguish between a core dichotomy of imperfective and perfective aspects. This dichotomy is present in almost all verbs and their nominalizations. The perfective is used to describe actions or states which are considered "complete, completed, total, or unified, or with a reference to a specific location in space and time, or to the completion of a specific goal". By contrast, imperfective forms describe those "which are incomplete, still in progress, repeated or habitual". Aspectual systems throughout the Slavic language family differ; the South Slavic languages are generally considered to have the most complex aspectual systems.
Certain kinds of adverbs and semantic domains tend to prefer one form or another. For example, adverbs meaning "at once" or punctual verbs such as "to kill" are associated with the perfective. In general, the perfective form is considered the marked form; the imperfective is typically used if an action is not explicitly designated as "completed". In West and East Slavic, present-tense inflections on perfective verbs are used to indicate a future tense. In the South Slavic language Serbo-Croatian, for example, the term ('I [often] come') contrasts with its East Slavic Russian counterpart (, 'I will reach').
Formation
In general, Slavic verbal vocabularies are composed of aspectual pairs, where two words share a lexical definition, but differ in their grammatical aspect. The formation of perfective–imperfective pairs is based on two processes. Perfectives are typically based on the addition of a perfectivizing prefix, a prefix added to a root imperfective simplex verb – that is, an unaffixed root verb which expresses an imperfective function – in order to form its perfective counterpart. In general, simplex verbs tend to be imperfective and atelic, meaning they do not have a clear endpoint in time. Examples of this include the imperfective Russian simplex verb (, 'to write') and its perfective counterpart (, 'to write'). Typically, perfective simplex verbs express punctual or bounded events. If a perfective verb already contains a prefix which changes its meaning outside of its aspect, a suffix may be used instead to imperfectivize it. For example, the Russian verb (, 'to constitute, to compose') is imperfectivized as (, 'to constitute, to compose'). The latter approach is much more common, accounting for about sixty-four percent of all perfective–imperfective pairs.
Alternations may also occur as a result of a change in aspect in lieu of a prefix; these alternations may include changes in vowel quality (including deletion), vowel length, and stress. Not all verbs have matching pairs, however; some imperfectives may not have a strictly perfective equivalent and vice versa. Examples include Ukrainian (, 'to cost'), which has no perfective counterpart, and (, 'to grasp'), which has no imperfective equivalent. In some rare cases, pairs may also exist through suppletion. Examples include Serbo-Croatian perfective against its imperfective counterpart , and ('to approach') against . A handful of other pairs are formed through changes in stress, as in the Ukrainian imperfective (, 'to fill in') with stress on the third syllable, as compared with its perfective counterpart () with stress on the second.
The application of perfectivizing prefixes has also led to alternative or specialized forms. For example, the Ukrainian verb (, 'to arrest') was perfectivized to () with the prefix (), but the perfectivized form has been re-imperfectivized as () with the suffix (). Similarly, Russian verbs have taken on more complex semantic functions with affixal stacking. The base first-person singular forms (, 'I pour') and (, 'I poured') contrast with the perfectivized forms (, 'I [will] pour') and (, 'I poured out'), respectively; these forms are further complexified by reimperfectivizing suffixes: () and (), both meaning 'I poured out' as matched with the previous respective pair.
The first objective method for determining aspectual pairs was devised by the Soviet linguist for Russian. Departing from the morphological view of Alexey Shakhmatov, Maslov recognized that narrative structures could be told either as a perfective past tense, as in (, 'John met Peter'), or as an imperfective historical present, as in (, 'John is meeting Peter'). This process, known as Maslov's criterion, can establish pairs based on this difference in usage rather than on the morphological derivation. The British scholar of Russian , however, criticized Maslov's view, arguing that it was not consistent with language use in Russian. Instead, he argued for a test, known as Forsyth's modal test, based on the use of imperatives, which tend to be perfective, as in (; 'Read that letter'), unless they are negative imperatives, as in (; 'Don't read that letter'). Forsyth's modal test has similarly been criticized for being contrary to actual language use, though it can serve as another prong in pair testing.
Imperatives Imperatives are found using both perfective and imperfective forms, though the use of one or the other semantically is somewhat variable. In general, non-negative imperfective usage may indicate politeness, though it may also indicate vulgarity and urgency as well. Perfective usage may show completion, as in other verbal constructions, but may be rudely abrupt or more neutrally polite. In Russian, for example, the perfective form (, 'sit down!') contrasts with the imperfective (, 'be seated!'). In Czech, the use of perfective imperatives tend to express a lack of agency by the subject over the outcome, such as getting a cold.
Sociolinguistic considerations may also be involved. The Russian perfective form, for example, implies a kind of social distance, giving a neutral tone in terms of politeness in formal contexts; the imperfective, by being less distant, can be perceived as extremely polite or extremely rude depending on context. For example, when the speaker is in a position to grant permission, the imperfective form of 'to open' can signal begrudging acquiescence by itself or strong encouragement with an adverb like (, 'of course'). Conversely, its perfective counterpart can signal neutral acquiescence or mild encouragement. Russian, however, is unique in this way; no other Slavic language allows the imperfective in these contexts. The Russian linguist attributes this imperfective use as a social understanding between the speaker and interlocutor that the interlocutor has already decided to carry out the action at hand, showing that the "gruff acquiescence" is something akin to resignation whereas the strong encouragement signals support. The Italian linguist , on the other hand, suggests that the imperfective signals the beginning of or in the middle of the action and the perfective signals its result. The implication of politeness thus derives from the speaker's implied distance from the action itself.