How to say "treacherous" in Japanese
Choosing the right word
- 佞姦ねいかんna-adjective, nounCovers 'treacherous' in the sense of a deceitful, disloyal person — cunning, wicked, perverse. It suits a scheming figure whose smooth manner hides disloyalty, but being uncommon, it is seldom the word you actually need.
- 悪逆無道あくぎゃくむどうna-adjective, no-adjectiveA four-character idiom condemning someone or their deeds as heinous, atrocious and disloyal; 'treacherous' here shades into 'treasonous'. Typical of strong condemnation of a tyrant or villain.
- 油断ならないゆだんならないexpression, i-adjectiveCovers 'treacherous' as 'you cannot let your guard down': a person or situation that seems safe but is sneaky, untrustworthy or dangerous. Fits a seemingly friendly colleague who might deceive you.
- 油断のならないゆだんのならないexpression, prenominal modifierIdentical in meaning to 油断ならない — the difference between the two is grammatical, not one of sense. Covers 'treacherous' as sneaky and untrustworthy: someone who seems harmless but might turn on you.
- 悪逆非道あくぎゃくひどうnoun, na-adjectiveA four-character idiom condemning deeds as heinous, atrocious, diabolic; 'treacherous' here is the treasonous sense. A close synonym of 悪逆無道, used to condemn a villain or tyrant.
For a sneaky, untrustworthy person or situation you must not relax your guard around, use 「油断ならない」／「油断のならない」; for a deceitful, disloyal person, 佞姦; for heinous, treasonous wickedness, the two four-character idioms.
Usage comparisons are AI-assisted and cross-checked by multiple models; for study reference only
Japanese equivalents
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