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A cognitive disorder marked by an impaired ability to comprehend or express language in its written or spoken form. This condition is caused by diseases which affect the language areas of the dominant hemisphere. Clinical features are used to classify the various subtypes of this condition. General categories include receptive, expressive, and mixed forms of aphasia.

A weakening or loss of the faculty of language in any of its forms-reading, writing, speaking, and the appreciation of the written, printed, or spoken word-independent of disease of the vocal organs or of the mind.

Inability to speak due to injury to speech-centres.

In pathol. a symptom of certain morbid conditions 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 only the loss of a few. 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 Ms 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.

Loss of the power of speech, or of coherent speech.

Loss of power of expression.

Defect or loss of the power of expression by speech, writing, or signs.

An impairment of the power of intellectual expression due to lesions in the brain.