Questions & Answers about Я сел на диван, затем прочитал письмо.
What is the infinitive form of сел, and what is its imperfective counterpart?
The verb сел is the past tense masculine singular of the perfective infinitive сесть (“to sit down”). Its imperfective counterpart is садиться, which you’d use for ongoing or habitual actions of sitting down.
Why is сел used here instead of садился?
Because сел (from perfective сесть) indicates a single, completed action. садился (imperfective) would imply the process of sitting down or a repeated/habitual action rather than one finished event.
Why is на диван in the accusative case, and what form would you use to say you’re already sitting on the couch?
When на expresses motion toward or onto something, Russian uses the accusative case. To describe location (already on the couch), you switch to the prepositional case: на диване.
Why is я omitted before прочитал письмо in the second clause?
Russian is a pro-drop language: if the subject is clear and stays the same, you can drop the pronoun. Since “I” is already established in the first clause, я isn’t needed again.
What does затем mean, and how does it differ from or ?