В музее мы рассматривали старинную картину.

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Breakdown of В музее мы рассматривали старинную картину.

• мы: we
• музей: the museum
• старинный: old (antique)

Questions & Answers about В музее мы рассматривали старинную картину.

Why is it в музее and not в музей?

Because this sentence describes location, not movement.

• в музее = in the museum / at the museum
• в музей = into the museum

After в, Russian uses:

• prepositional case for being somewhere
• accusative case for motion into somewhere

So here, since we were looking at a painting in the museum, the correct form is в музее.

Why does музей change to музее?

Музей is the dictionary form, called the nominative singular.

After в when it means in/at, the noun goes into the prepositional case:

• музей → в музее

This is a normal pattern for many masculine nouns. The ending changes to show the noun’s role in the sentence.

Why is it картину and not картина?

Because картину is the direct object of the verb рассматривали.

In Russian, direct objects often go into the accusative case.
For a feminine noun ending in -а, the accusative singular usually changes like this:

• картина → картину

So:

• картина = a painting, the painting
• рассматривали картину = were looking at/examining the painting