Carelessness means not paying enough attention to what you're doing, which often leads to mistakes or accidents. When you rush through your homework without checking your work, that's carelessness. When you leave your bike unlocked outside or forget to close the gate so your dog gets out, those are acts of carelessness.

Careless people aren't necessarily lazy or uncaring. They might simply be distracted, moving too fast, or thinking about something else while they work. A careful student double-checks their math problems and reads instructions twice. A careless student skips steps, assumes they know what to do, and hands in work with easily avoidable errors.

The consequences of carelessness range from minor to serious. Careless spelling might cost you points on an essay. Careless driving can cause accidents. Scientists must avoid carelessness in their experiments, or their results will be unreliable. Surgeons, pilots, and engineers can't afford to be careless because lives depend on their precision.

The opposite of carelessness is attentiveness or diligence: taking your time, focusing on what matters, and giving your best effort to do things right. Many mistakes that people blame on bad luck are actually the result of carelessness that could have been prevented with a moment's extra thought.