Learn Russian: Завтра утром солнце взойдёт очень рано. - Tomorrow morning the sun will rise very early.

The verb взойти (to rise) uses the upward motion prefix вз-. Because the base verb starts with a tricky consonant cluster, an extra -о- is added to make it easier to say, resulting in взо-. Russian poetically treats the sun rising as walking up into the sky, so it uses a prefix attached to the base verb for going on foot!

Why is the verb spelled with a д (взойдёт) if the infinitive is взойти?

Verbs of motion built on идти (to go on foot) have an irregular conjugation pattern. In the present or simple future tense, a hidden д reappears. Just like идти becomes он идёт, the perfective verb взойти becomes солнце взойдёт.

Why do we use the perfective verb взойдёт here instead of the imperfective всходить?

The sentence refers to a single, specific, completed event happening tomorrow morning. If you wanted to talk about a repeated or habitual action, like saying the sun always rises early in the summer, you would use the imperfective form всходит.

Why does the word for morning end in -ом (утром)?