aphasia vs brain disorder

aphasia and brain disorder both are nouns.

Word	Noun	Adjective	Verb	Adverb
aphasia	Yes	No	No	No
brain disorder	Yes	No	No	No

As nouns, brain disorder is a hypernym of aphasia; that is, brain disorder is a word with a broader meaning than aphasia:

aphasia: inability to use or understand language (spoken or written) because of a brain lesion
brain disorder: any disorder or disease of the brain

Other hypernyms of aphasia include brain disease, encephalopathy.

aphasia (noun)	brain disorder (noun)
inability to use or understand language (spoken or written) because of a brain lesion	any disorder or disease of the brain