Вчерашняя ссора оказалась пустой, и мы смеялись над ней за ужином.

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Breakdown of Вчерашняя ссора оказалась пустой, и мы смеялись над ней за ужином.

• ужин: the dinner
• мы: we
• оказаться: to turn out

Questions & Answers about Вчерашняя ссора оказалась пустой, и мы смеялись над ней за ужином.

What is the difference between вчерашняя ссора and just using вчера with ссора? Could I say Вчера ссора оказалась пустой?

Вчерашняя is an adjective meaning “yesterday’s”, formed from вчера (“yesterday”).

• Вчерашняя ссора = the quarrel that happened yesterday (it identifies which quarrel).
• вчера is an adverb = yesterday (it tells when something happened).

Your version Вчера ссора оказалась пустой is grammatically possible, but it means:

• Yesterday the quarrel turned out to be pointless (the time of “turning out” is yesterday).

The original sentence with вчерашняя ссора talks about that specific quarrel from yesterday; it doesn’t specify when you realized it was pointless (maybe today, maybe later). So:

• вчерашняя ссора — focuses on which quarrel.
• вчера ... оказалась — focuses on when it turned out to be pointless.

Both are correct, but the nuance is different.

Why is it оказалась and not just была? What does оказаться add?