An epileptic seizure (colloquially a fit) is a brief episode of signs or symptoms due to abnormal excessive or synchronous neuronal activity in the brain. The outward effect can vary from uncontrolled jerking movement (tonic-clonic seizure) to as subtle as a momentary loss of awareness (absence seizure). Diseases of the brain characterized by an enduring predisposition to generate epileptic seizures are collectively called epilepsy.
Seizures can also occur in people who do not have epilepsy for various reasons including brain trauma, drug use, elevated body temperature, hypoglycemia (low blood sugar levels) and hypoxia (low levels of oxygen to the brain). Additionally, there are a number of conditions that look like epileptic seizures but are not.