Ночью ветер дует сильнее, чем днём.

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Breakdown of Ночью ветер дует сильнее, чем днём.

• ночью: at night
• ветер: the wind
• днём: during the day

Questions & Answers about Ночью ветер дует сильнее, чем днём.

Why is ночью in the instrumental case?

In Russian, some time expressions use the instrumental case to mean at a certain time / during a period, especially with parts of the day or seasons.

So:

• ночь = night
• ночью = at night

This is a fixed and very common adverb-like use.

Compare:

• утром = in the morning
• днём = in the daytime / during the day
• вечером = in the evening
• ночью = at night

Even though instrumental often has other meanings too, here it simply tells you when something happens.

Why is it днём, not днем?

Both spellings may appear in writing, but днём is the version with the correct pronunciation marked by ё.

• день = day
• instrumental form: днём

The letter ё is often written as е in everyday texts, but it is still pronounced yo. So:

• written fully: днём
• often seen in less careful spelling: днем
• pronunciation: roughly dnyom

For learners, it is very helpful to remember the ё, because it shows both the sound and the stress.