〜のに
And yet, even though… (a result contrary to expectations)machine translation
FormationPlain form + のに (nouns and な-adjectives + なのに)
のに joins two clauses where the second runs CONTRARY to what the first led us to expect, with a feeling of surprise, regret, or dissatisfaction: 薬を飲んだのに、熱が下がりません (I took medicine, and yet the fever won't go down). The connection works like ので: plain form; nouns and な-adjectives take なのに.
のに differs from けど・が in emotional load: けど is just a neutral "but," while のに always carries the sense of "it should have been otherwise!" That's why the clause after のに can't be a command, invitation, or statement of intent — things that haven't happened yet; use けど・が there instead.
のに can also end a sentence, trailing off in regret: せっかく作ったのに… (after all the trouble I took making it…). This reproachful nuance is fairly strong, so be careful using it with superiors.
Examples
薬を飲んだのに、熱が下がりません。
I took the medicine, and yet the fever still won't go down.
日曜日なのに、仕事をしなければなりません。
It's Sunday, and yet I still have to work.
たくさん勉強したのに、試験に落ちました。
I studied so much, and yet I still failed the exam.