Я познакомился с новым соседом, когда он переезжал.

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Breakdown of Я познакомился с новым соседом, когда он переезжал.

• с: with
• новый: new
• когда: when
• он: he
• сосед: the neighbor
• познакомиться: to meet
• переезжать: to move in

Questions & Answers about Я познакомился с новым соседом, когда он переезжал.

Why is the verb познакомился in the perfective aspect here, instead of the imperfective знакомился?

The perfective познакомился indicates a single, completed action: “I got to know” or “I met.” The imperfective знакомился would suggest an ongoing or habitual process (“I was getting to know” or “I used to meet”), which doesn’t fit because the speaker describes one specific event that finished.

Why does знакомиться use the preposition с?

In Russian, познакомиться (to get acquainted) always takes с + instrumental case to mark the person you’re meeting. So познакомиться с кем-то literally means “to become acquainted with someone.” Here с новым соседом = “with the new neighbor.”

Why is новым соседом in the instrumental case?

After the preposition с, the noun must be in the instrumental. Новый сосед (nominative) becomes новым соседом (instrumental) to match с.

Why is the subordinate verb переезжал (imperfective) used instead of the perfective переехал?

Imperfective aspect describes an action in progress or backgrounded action. Переезжал = “was moving” sets the scene for when the main event happened. If you used perfective переехал (“moved in”), you’d be saying the move was fully completed at that moment, changing the nuance.

Could you use переехал here, and how would the meaning change?

Yes:
Я познакомился с новым соседом, когда он переехал.
This means “I met my new neighbor after he had moved in.” The meeting happens once the move is finished, unlike the original, where the meeting occurred during the move.

Is the word order fixed, or can I say Когда он переезжал, я познакомился с новым соседом?

Word order in Russian is flexible. Starting with the time clause—Когда он переезжал, я познакомился с новым соседом—is perfectly fine. It emphasizes the timing slightly more but conveys the same overall meaning.