careless
adj.adj. not giving enough attention or thought to what you are doing. You use this when someone makes a mistake because they are not being careful.
adj. failing to give sufficient attention, effort, or thought to a task or situation. Often used to describe actions or people that result in avoidable errors.
He made a few careless mistakes on the math test.
Leaving the front door unlocked was a careless oversight that worried the rest of the family.
The report was marred by careless formatting and several factual inconsistencies that suggested a lack of thorough proofreading before the final submission.
From Middle English careles, from Old English carlēas (“careless, reckless, void of care, free from care, free”), equivalent to care + -less. Cognate with Icelandic kærulaus (“careless, negligent”).
Commonly followed by the preposition 'with' when referring to resources or 'about' when referring to attitudes.
He is careless of his workHe is careless with his workWhen describing how someone handles a task or object, 'careless with' is the standard collocation.