Aphasia is an impairment that affects the ability to read, write, and understand speech. Typically, symptoms occur after a traumatic brain injury, stroke, or brain tumor. There are three classifications of aphasia: nonfluent, fluent, or global. Nonfluent aphasia is damage to the left frontal lobe of the brain causing lack of verbal communication despite auditory comprehension; where as fluent aphasia allows one to speak, but unintelligibly due to damage in the middle left side of the brain. Global affects both verbal expression and comprehension caused by severe damage to to the brain's language network.