Learn Hardcore Russian: Повелительное наклонение совершенного вида часто оканчивается на –и и обозначает единовременное или завершённое действие, например: прочитай книгу. - The perfective imperative often ends with –и and indicates a single or completed action; for example: finish reading the book.

In Russian grammar повелительное наклонение is the imperative mood. It’s used to give commands, instructions or requests (e.g., “sit down,” “read this,” “please close the door”).

What does совершенного вида mean?

Совершенный вид is the perfective aspect in Russian. It indicates that an action is viewed as a complete whole or a one-time event. In contrast, the imperfective aspect (несовершенный вид) describes ongoing, habitual or repeated actions.

What does the suffix –и signify in the perfective imperative?

When you form the 2nd person singular imperative of many perfective verbs, you attach –и to the verb stem. This ending signals both the imperative mood and the perfective aspect.
Example:
• спросить → спроси
• написать → напиши

Why does the example прочитай книгу end with –ай instead of just –и?

Прочитать belongs to the first conjugation, where the consonant stem resists a direct –и. Instead, you insert the syllable –ай (with –й functioning as a variant of –и after a). So the pattern is:
прочита́ть (infinitive) → прочита́й (2 sg. imperative) → прочитай книгу.

What is meant by единовременное действие and завершённое действие?

Единовременное действие (“one-time action”) means the command asks for a single occurrence of the action.
Завершённое действие (“completed action”) stresses that the action must be carried out to its end.
In our example, прочитай книгу tells someone to read the entire book through once.

How does the perfective imperative differ from the imperfective imperative?

• Perfective imperative (прочитай) demands a single or completed action (“finish reading”).
• Imperfective imperative (читай) either invites beginning, continued, or repeated action (“start reading,” “keep reading,” or “read regularly”).

How do you form the plural (or polite) form of a perfective imperative?

Attach –те to the singular imperative stem. For example:
прочитай → прочитайте (you pl. or polite you sg.)
This ending is exactly the same as for imperfective verbs; the difference lies in the stem you choose (perfective vs. imperfective).

Are there exceptions to the rule that perfective imperatives end in –и?

Yes. While many perfective verbs use –и, others follow different patterns or are irregular:
• Some take –ай (прочитай, расскажи).
• A few change the vowel or consonant (дать → дай, съесть → съешь).
• Verbs with certain stem endings may require –й or even –ь.
Always check a good verb table or dictionary for irregular imperatives.