How to say "imperfect" in Japanese

• 不全ふぜんCommon
  na-adjective, no-adjectiveSeldom the word you want for plain 'imperfect': it appears chiefly in medical and technical expressions for an organ or function that fails to work properly — the 'partial, incomplete' side of the meaning.
  システムのこの予測よそくされなかった機能きのう不全ふぜんは不適切ふてきせつな配線はいせん系統けいとうによって引き起ひきおこされた。↗

  This unexpected malfunctioning of the system was caused by improper wiring.
• 不完全ふかんぜんCommon
  na-adjective, nounThe closest general equivalent: use it when something is imperfect in the sense of flawed, faulty, or incomplete — a system, copy, or understanding that is less than perfect.
  彼かれの計画けいかくはまだ不完全ふかんぜんな点てんが多おおい。↗

  His plan leaves much to be desired.
• 不十分ふじゅうぶんCommon
  na-adjective, nounCovers 'imperfect' when it means not enough or inadequate — preparations, evidence, or information that fall short of what is needed, rather than something flawed in itself.
  これらの２つの分子ぶんしが異ことなったスピードで動うごいていることを示しめすだけでは不十分ふじゅうぶんである。↗

  It is not enough to show that these two particles are moving at different speeds.
• 未完成みかんせいCommon
  no-adjective, na-adjectiveUse for 'imperfect' in the sense of unfinished or incomplete: a work, plan, or product that is still in progress or has not reached its final form.
  私の仕事しごとはまだ未完成みかんせいです。↗

  My work is not complete yet.

Choose 不完全 for the general sense of flawed or defective, 不十分 when something falls short or is inadequate, 未完成 for unfinished works, and 不全 chiefly in medical and technical expressions for failing organs or functions.

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

• 不全ふぜんpartial
• 不完全ふかんぜんimperfect
• 不十分ふじゅうぶんinsufficient
• 未完成みかんせいincomplete
• 至らないいたらないimperfect
• 至らぬいたらぬimperfect
• 訳ありわけありhaving special circumstances (e.g. problems, issues, advantages, flaws, defects, etc.)
• 片端かたわimperfect
• 片かたincomplete
• 未完了みかんりょうimperfect