Утром на крыше висели длинные сосульки, а под окном вырос высокий сугроб.

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Breakdown of Утром на крыше висели длинные сосульки, а под окном вырос высокий сугроб.

• окно: the window
• длинный: long
• под: under

Questions & Answers about Утром на крыше висели длинные сосульки, а под окном вырос высокий сугроб.

Why is утром in the instrumental case?

Russian often uses the instrumental case for parts of the day when they function like adverbs of time. So утром means in the morning. This is a very common pattern:

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

Here, the instrumental does not mean an instrument; it is just the standard form in this time expression.

Why is it на крыше, not на крышу?

Because this sentence describes location, not movement.

With на:

• на + prepositional = location, on / at
• на + accusative = motion toward a place, onto / to

So:

• на крыше = on the roof where something already is
• на крышу = onto the roof with movement

Since the icicles are hanging there, Russian uses на крыше.

Why is it под окном? What case is окном?