Learn Hardcore Russian: Я прочитаю письмо, когда вернусь домой. - I will read the letter when I return home.

Russian verbs have two aspects: perfective (completed actions) and imperfective (ongoing or habitual actions).
прочитаю is the perfective future of прочитать (“to read to the end”).
вернусь is the perfective future of вернуться (“to return/come back”).
Using perfective indicates that you will complete both actions. If you said буду читать письмо, it would mean “I will be reading the letter” (ongoing), not necessarily finishing it.

Why is there a comma before когда?

In Russian, when a main clause is followed by a subordinate clause (introduced by conjunctions like когда, что, потому что), you must separate them with a comma. Here, Я прочитаю письмо is the main clause, and когда вернусь домой is the subordinate time clause.

Why do we use the future tense in the subordinate clause когда вернусь домой instead of the present, as we do in English?

In English, we often say “I’ll read it when I get home” (present after when). In Russian, time clauses referring to the future require the future tense in both clauses. You cannot use the present tense for future events after когда.

What case is письмо, and why?

письмо is in the accusative case because it is the direct object of the verb прочитаю. It’s a neuter inanimate noun, so its accusative form is identical to the nominative (письмо).

What part of speech is домой, and how does it differ from в дом or дома?

домой is a directional adverb meaning “toward home.”
в дом uses the preposition в
- accusative to mean “into the house” (emphasis on entering a building).
дома is either the adverb “at home” or the genitive singular of дом, depending on context.

Is the pronoun я necessary here?

No, Russian allows dropping subject pronouns (pro-drop) because the verb ending -ю in прочитаю already shows the 1st person singular. Я can be included for emphasis or clarity but is not required.

Could I say Я буду читать письмо, когда вернусь домой instead?

You can, but it changes the nuance. Я буду читать письмо (future imperfective) emphasizes the action in progress (“I will be reading”). Я прочитаю письмо (future perfective) emphasizes the completion (“I will read it [to the end]”). Choose based on whether you care about finishing the reading or just the act itself.

How do you pronounce прочитаю and вернусь? Where is the stress?

прочитаю [pra-chi-TA-yu] – stress on the third syllable: чита́.
вернусь [ver-NÚsʹ] – stress on the second syllable: ну́сь.

Could I use после того как я вернусь домой instead of когда вернусь домой?

Yes. после того как я вернусь домой literally means “after I return home.” It’s a bit longer and explicitly means “after,” but grammatically it’s correct:

• Я прочитаю письмо, после того как вернусь домой.