savant syndrome vs subnormality

savant syndrome and subnormality both are nouns.

Word	Noun	Adjective	Verb	Adverb
savant syndrome	Yes	No	No	No
subnormality	Yes	No	No	No

As nouns, subnormality is a hypernym of savant syndrome; that is, subnormality is a word with a broader meaning than savant syndrome:

savant syndrome: A condition in which a person with a mental disability, such as an autism spectrum disorder, demonstrates profound and prodigious capacities or abilities far in excess of what would be considered normal.
subnormality: lack of normal development of intellectual capacities

Other hypernyms of savant syndrome include brilliance, genius, backwardness, mental retardation, retardation, slowness.

savant syndrome (noun)	subnormality (noun)
A condition in which a person with a mental disability, such as an autism spectrum disorder, demonstrates profound and prodigious capacities or abilities far in excess of what would be considered normal.	lack of normal development of intellectual capacities
	the state of being less than normal (especially with respect to intelligence)