According to their aspect, verbs can be:
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- imperfective - used for actions that are repeated or habitual; refered to in general or their entirety; or for actions that last a long time.
- perfective - used for actions that happen one time; where the focus is on a part of the action, such as its completion, lack thereof, or beginning; and for actions that take a short time.
In this unit, three past tenses are introduced:
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- imperfect - made from imperfective verbs and used for describing witnessed past actions that are repeated or habitual; referred to in general or their entirety; or for actions that last a long time.
- aorist - made from perfective verbs and used for describing witnessed actions that happen one time; where the focus is on a part of the action, such as its completion, lack thereof, or beginning; and for actions that take a short time.
- l-past - made from both imperfective and perfective verbs and used for describing unwitnessed past actions; or for discussing whether or not an action ever took place; or for expressing doubt, disbelief, or surprise.
The imperfect and aorist are formed from the dictionary form of the verb, by changing the final vowel (if dictated by the rules you will learn in this unit) and adding the appropriate endings.
The l-past is formed with a helping (or auxiliary) verb (сум, to be) and a main verb (describing the action). The verb сум is used in the present tense, whereas the main verb is used in its l-form. The l-form is formed from the dictionary form of the verb, by changing the final vowel (if dictated by the rules you will learn about in this unit) and adding the appropriate endings.