Aphasia, a fa'zhe a, a symptom of certain diseases of the nervous system, in which the patient loses the power of expressing ideas by means of words, or loses the appropriate use of words, the vocal organs the while remaining intact and the intelligence sound. There is sometimes an entire loss of words as connected with ideas, and sometimes the loss of a few only. In one form of the disease, called aphemia, the patient can think and write but cannot speak; in another, called agraphia, he can think and speak, but cannot express his ideas in writing. In a great majority of cases, where post-mortem examinations have been made, morbid changes have been found in the left frontal convolution of the brain.