无效 wúxiào not valid
not valid; ineffective; in vain
How to remember 无效: 无 have not + 效 result = not valid.
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How it is used
- Means "invalid / ineffective" - 这张票已经无效 (zhè zhāng piào yǐjīng wúxiào) this ticket is no longer valid; 治疗无效 (zhìliáo wúxiào) the treatment had no effect.
- Direct antonym of 有效 (yǒuxiào, valid/effective); common on documents, contracts, and in medical/legal contexts - 护照有效 (hùzhào yǒuxiào) the passport is valid.