効く・利く|きくkiku[0]heiban (flat)
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Which spelling to use
効く効く is the more common written form of this verb and the recommended default for beginners; use it when writing about something being effective or taking effect.
利く利く is a less common written form of the same verb; you may encounter it, but beginners should generally choose 効く instead.
Definitions
- godan verb, intransitive verbto be effective; to take effect; to be good (for)usu. 効く
- godan verb, intransitive verbto work; to function wellusu. 利く for body senses, functions, etc.
- godan verb, intransitive verbto be possible (to do, use, etc.); to be able to
- godan verb, transitive verbto taste (alcohol); to try
Conjugation
| Dictionary form | 効く（きく） |
|---|---|
| Polite (masu) | 効きます（ききます） |
| Negative (nai) | 効かない（きかない） |
| polite (masen) | 効きません（ききません） |
| classical zu / nu | 効かず・効かぬ（きかず・きかぬ） |
| Past (ta) | 効いた（きいた） |
| polite (mashita) | 効きました（ききました） |
| Past negative (nakatta) | 効かなかった（きかなかった） |
| polite (masen deshita) | 効きませんでした（ききませんでした） |
| Te form | 効いて（きいて） |
| Potential | 効ける（きける） |
| Passive | 効かれる（きかれる） |
| Causative | 効かせる（きかせる） |
| Causative passive | 効かせられる・効かされる（きかせられる・きかされる） |
| Conditional (ba) | 効けば（きけば） |
| tara | 効いたら（きいたら） |
| Volitional | 効こう（きこう） |
| polite (mashou) | 効きましょう（ききましょう） |
| Imperative | 効け（きけ） |
Common forms generated by rule; see the senses for honorific or irregular usage.
Transitive / intransitive pair
薬が効く
薬を効かす
効く describes something producing its effect naturally (薬が効く 'the medicine works'), while 利かす means to deliberately make something effective or exert its effect (薬を効かす 'make the medicine take effect').
Usage comparisons are AI-assisted and cross-checked by multiple models; for study reference only
Synonyms & antonyms
- Antonym無効むこうNeutralAn antonym of 「効く」: invalid, void, or lacking effect, as in 「無効な契約」「無効な対策」. Leans formal; 「効かない」 is the more colloquial, concrete way to say something has no effect.
- Antonym効かないNeutralThe negative form of 「効く」: something has no effect or doesn't work, as in 「薬が効かない」. Neutral in tone, it simply states the opposite of the headword.
For a drug or measure taking effect, write 「効く」; for something functioning well, write 「利く」. Say 「効かない」 when something has no effect; 「無効」 is the formal word for something void or no longer effective.
Usage comparisons are AI-assisted and cross-checked by multiple models; for study reference only
Japanese definitions
Kanji in this word
See also
