不当|ふとうfutou[0]heiban (flat)

1. na-adjective, noununfair; unjust; wrongful; improper; unreasonable; unwarranted; unjustified; undeserved; undue
   その女性じょせいは不当ふとうに私を責せめた。↗

   That woman has wrongly accused me.

• Synonym不正ふせいNeutralNeutral term for wrongdoing or cheating, as in 「不正行為」; leans toward rule-breaking and fraud, while 「不当」 stresses unreasonableness or impropriety.
• Synonym不公平ふこうへいNeutralNeutral word for unfairness, as in 「不公平な扱い」; focuses on uneven or biased treatment.
• SynonymアンフェアNeutralNeutral loanword for unfair; leans colloquial and is common in sports talk.
• Related不法ふほうWrittenWritten/formal prose for unlawful, as in 「不法侵入」; centers on illegality.
• Related非道ひどうWrittenWritten/formal prose for cruel, inhuman behavior, as in 「非道な行い」; much stronger in degree.
• Related悪質あくしつNeutralNeutral word for vicious or malicious, as in 「悪質な業者」; carries a strongly negative judgment.
• Related不適当ふてきとうNeutralNeutral word for inappropriate, as in 「不適当な表現」 or 「不適当な人選」; stresses unsuitability.
• Related不適ふてきWrittenWritten/formal prose for unsuitable, as in 「使用に不適」 or 「不適と判断する」; stresses being unfit for the purpose.
• Related邪よこしまWrittenWritten/formal prose for wicked or perverse, as in 「邪な考え」; stresses corruption of the heart or intentions.
• Related不義ふぎWrittenWritten/formal prose for unrighteous conduct or adultery; carries an old-fashioned flavor.
• Related不平等ふびょうどうNeutralNeutral word for unequal, as in 「不平等条約」; focuses on disparities in status or position.
• Related不届きふとどきWrittenWritten/formal prose for rude or disgraceful behavior, as in 「不届き者」; centers on personal conduct.
• Related偏頗へんぱWrittenWritten/formal prose for favoritism or bias; rare in modern usage.
• RelatedえこひいきNeutralColloquial word for favoritism or playing favorites, as in 「えこひいきする」.
• Related失当しっとうWrittenWritten/formal prose for improper handling of matters; few examples of use.
• Related不道徳ふどうとくNeutralNeutral word for immoral, as in 「不道徳な行為」; centers on ethics, while 「不当」 centers on unreasonableness.
• Related不徳義ふとくぎWrittenWritten/formal prose for dishonest or bad-faith conduct; a moral judgment.
• RelatedアンモラルNeutralNeutral loanword for something lacking morals; leans toward literary and art criticism.
• RelatedインモラルNeutralNeutral loanword for immoral; leans toward artistic or entertainment subject matter.
• Antonym妥当だとうNeutralAntonym: means valid and reasonable; the direct opposite of 「不当」.
• Antonym正当せいとうNeutralAntonym: means just and legitimate, as in 「正当な理由」; the direct opposite of 「不当」.

Use 「不当」 for what is unreasonable, unjust or improper; it is common in legal and news contexts, as in 「不当解雇」 and 「不当な扱い」. For cheating or fraud say 「不正」, for unlawful acts 「不法」, and for uneven treatment 「不公平」. 「正当」 and 「妥当」 are its antonyms. The remaining words cover narrower shades, such as favoritism, immorality or inappropriateness.

Usage comparisons are AI-assisted and cross-checked by multiple models; for study reference only

1. 道理どうりに合あわないこと。妥当だとうでないこと。公正こうせいでないこと。