莫非: could it be that…?
副词 / adverbs
Tone colorsā tone 1á tone 2ǎ tone 3à tone 4a neutral
莫非 + hypothesis + (不成/吗)？
莫非 expresses a surprised or worried guess in question form: "Could it be that…?", "Don't tell me…?". The speaker suspects an unexpected explanation.
It often ends with 吗 or 不成 (more literary): 莫非他生病了不成？ Close to 难道, but 难道 = reproach/obviousness, 莫非 = a genuine hypothesis.
Examples
他今天一句话也没说，莫非有什么心事？
Tā jīntiān yí jù huà yě méi shuō, mòfēi yǒu shénme xīnshì?He hasn't said a word today: could something be bothering him?
莫非人生本来就没有标准答案？
Mòfēi rénshēng běnlái jiù méiyǒu biāozhǔn dáàn?Could it be that life simply has no standard answer?
门开着，灯也亮着，莫非有人来过不成？
Mén kāi zhe, dēng yě liàng zhe, mòfēi yǒu rén lái guo bùchéng?The door's open and the light's on: could someone have been here?
Common mistakes
✗ 莫非 as a reproach: ✗ 莫非你不知道？ (meaning "surely you know!") → ✓ 难道你不知道？
✗ Dropping the question form: 莫非 requires a question.