subnormality vs slowness

subnormality and slowness both are nouns.

Word	Noun	Adjective	Verb	Adverb
subnormality	Yes	No	No	No
slowness	Yes	No	No	No

As nouns, subnormality and slowness are synonyms defined as:

subnormality and slowness: lack of normal development of intellectual capacities

Other synonyms of subnormality include backwardness, mental retardation, retardation.

subnormality (noun)	slowness (noun)
lack of normal development of intellectual capacities	a rate demonstrating an absence of haste or hurry
the state of being less than normal (especially with respect to intelligence)	lack of normal development of intellectual capacities
	unskillfulness resulting from a lack of training