A stroke is the loss of brain function(s) due to inadequate blood supply to the brain. This can be due to ischemia (lack of blood supply) caused by thrombosis or embolism(a small blood clot that blocks the arteriole) or due to a hemorrhage. As a result, the affected area of the brain is unable to function, leading to inability to move one or more limbs on one side of the body, inability to understand or formulate speech, or inability to see one side of the visual field.