A calm, untroubled state about something that other people find worrying. It is a noun, and it is not the same as simply not knowing — the situation is there, you have seen it, and it does not disturb you. That is why the word almost always carries a hint of judgement from the speaker: *she watched the argument with complete unconcern* suggests the speaker thinks she perhaps should have cared. It often appears with *with*, *at*, or *about*: with unconcern, unconcern at the news, unconcern about the cost. Sometimes it is admiration — a doctor's unconcern in an emergency is steadiness. More often it is a mild criticism, close to indifference or coolness. It is a formal, literary word; in speech people say *he didn't seem bothered* or *she didn't care*. You will meet it most often in novels and in serious journalism, frequently in phrases like *an air of unconcern* or *studied unconcern* — that second one meaning the calm is put on for show, and the person actually does care underneath.

漠不關心、毫不在意（帶有「別人都在擔心，他卻無所謂」的意味，書面語）