Ночью я сплю спокойно.

At night I sleep peacefully.

Breakdown of Ночью я сплю спокойно.

• я: I
• ночь: the night
• спать: to sleep
• спокойно: peacefully

Questions & Answers about Ночью я сплю спокойно.

Why is the word ночью used instead of the dictionary form ночь?

In Russian, the noun ночь (night) takes the instrumental case (ночью) when you want to say “at night.” This case form turns the noun into an adverbial expression of time. You wouldn’t say ночь я сплю спокойно, because ночью specifically conveys “during the night.”

Why is there no preposition like в before ночью?

For parts of the day, Russian typically drops the preposition and uses the case ending alone. So you get утром, днём, вечером, ночью. Adding в ночью would be ungrammatical. If you really need a preposition, you’d use the genitive (в ночь) in rare poetic contexts, but the normal everyday form is ночью without в.

Can I omit the pronoun я since the verb сплю already shows “I”?

Yes. Russian verbs are conjugated to show their subject, so you can say simply Ночью сплю спокойно and it’s perfectly fine. Including я adds slight emphasis or clarity (“I, specifically, sleep peacefully at night”), but it’s not required.

What part of speech is спокойно, and why isn’t it спокойный?

Спокойно is an adverb. It answers the question “How?” (Как?). Adjectives (like спокойный) modify nouns, while adverbs modify verbs. Since сплю is a verb (“I sleep”), you need the adverbial form спокойно (“peacefully”).

Why is the verb сплю used here and not спит or another form?

Сплю is the first-person singular present tense form of спать (to sleep). If you were talking about he/she, you’d say он спит or она спит. But because the speaker refers to themselves, the correct form is я сплю.

Is the word order flexible? Could I say Я сплю спокойно ночью or Сплю ночью спокойно?

Russian word order is relatively free, but changing it shifts the emphasis:

• Ночью я сплю спокойно (neutral, time first)
• Я сплю спокойно ночью (focus on the subject and action, time as afterthought)
• Сплю ночью спокойно (emphasizes the peacefulness of the sleep) All are grammatically correct; you choose based on what you want to highlight.

How do I pronounce сплю спокойно and where are the stresses?

Pronunciation with stress marks:

• сплю́ [sp-lyú]
• спокóйно [spa-kóy-no]
  So it sounds like “splyú spa-kóy-no.”

Can I use a different adverb instead of спокойно, for example мирно?

Yes. Мирно is a close synonym meaning “peacefully.” You could say Ночью я сплю мирно. The nuance is very similar: спокойно focuses on being calm and untroubled, while мирно often implies “without disturbance” or “quietly.” Both are correct here.