Malfeasance is deliberately and with forethought committing an
illegal act (usually having to do with one's official
responsibilities). Nonfeasance is simply taking no action at all.
Misfeasance is defined as taking devious/questionable actions.
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Nonfeasance
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The word is used to mean "willfully inappropriate or incorrect action" and typically applies to a public official who misuses his office.
The much more common term is malfeasance, a willfully inappropriate action (or illegal action) that causes harm to a person or entity.