Delirium is an acute disturbance in attention, cognition, and awareness. It is diagnosed clinically using tools like the CAM. The presentation can be hyperactive or hypoactive. Risk factors include older age, frailty, cognitive impairment, and multiple medications. Prevention strategies focus on reorientation, mobility, sleep, and limiting psychoactive medications. Treatment aims to address underlying causes, though antipsychotics are not usually recommended. Delirium can increase mortality and institutionalization, so prompt recognition and management are important.