How to say "malpractice" in Japanese

• 背任はいにんCommon
  noun, suru verb, intransitive verbCovers malpractice in the legal sense of breach of trust: someone entrusted with another's affairs deliberately betrays that duty, typically for personal or a third party's gain. Essentially a legal term.
  某ぼう連盟れんめい元会長もとかいちょうが背任はいにんの容疑ようぎで逮捕たいほされました。↗

  The former president of a certain association has been arrested on suspicion of breach of trust.
• 不始末ふしまつCommon
  noun, na-adjectiveCovers malpractice as mismanagement or irregularity: careless or improper handling of money or official duties. Milder and vaguer than 背任, it suggests sloppiness in handling affairs rather than deliberate betrayal of trust.
  彼かれは部下ぶかの不始末ふしまつを見みつけた。↗

  He detected his men's misconduct.

Use 背任 for malpractice in the sense of deliberate breach of trust by someone in a responsible position, and 不始末 for milder mismanagement or irregularities; neither fits professional negligence such as medical errors.

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

• 背任はいにんbreach of trust
• 不正行為ふせいこういunfair practices
• 不始末ふしまつirregularity