Grammatical aspect

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" (the letters may still be unfinished).

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.

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.

(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 they "have eaten" or "have been eating". The present auxiliary implies that they are in some way present (alive), even when 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:

In the Tyrolean and other Bavarian regiolect the prefix *da can be found, which form perfective aspects. "I hu's gleant" (Ich habe es gelernt = I learnt it) vs. "I hu's daleant" (*Ich habe es DAlernt = I succeeded in learning).

Sometimes the meaning of the auxiliary verb is diminished to 'being engaged in'. Take for instance these examples:

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.

In rare cases corresponding telic and atelic forms can be unrelated by meaning.

ʔi=na-fane-naranara fei nara Faninilo ba, ʔaleʔena ba ini liai mei ramaʔa mei

3SG=REAL-HAB-think(REDUP) the thought Faninilo COMP like COMP who again the person the

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.

Other aspects in ASL include the following: stative, inchoative ("to begin to..."), predispositional ("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.