1A conjunction meaning "and yet" or "despite that," introducing a result that contradicts what was expected from what was just said. Often carries a stronger nuance of surprise or dissatisfaction than それでも.
何度も注意した。それなのに、彼はまた同じミスをした。
I warned him many times. And yet he made the same mistake again.
一生懸命勉強した。それなのに、テストの結果はよくなかった。
I studied really hard. Despite that, my test results weren't good.
約束の時間はとっくに過ぎていた。それなのに、彼女はまだ来なかった。
The agreed time had long since passed. And yet she still hadn't arrived.
天気予報では晴れると言っていた。それなのに、外は大雨だ。
The weather forecast said it would be sunny. Nevertheless, it's pouring outside.