What is the medical term for the inability to understand or produce speech?

The medical term for the inability to understand or produce speech is aphasia. This condition arises due to damage to the areas of the brain responsible for language processing, commonly following a stroke or brain injury. Aphasia can manifest in various forms, affecting a person's ability to speak, comprehend spoken language, read, and write, depending on the extent and location of the brain damage.

Dysphasia, while related, specifically refers to partial inability to express or understand language, distinguishing it from aphasia, which represents a more complete impairment. Verbal apraxia involves the difficulty in motor planning to produce speech sounds and is not a language comprehension issue. Speech delay refers to a slower than expected development of speech in children and does not encompass the broader inability to process language seen in aphasia. Thus, the term that accurately describes the condition of being unable to understand or produce speech is aphasia.