retardation vs subnormality

retardation and subnormality both are nouns.

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

As nouns, retardation and subnormality are synonyms defined as:

retardation and subnormality: lack of normal development of intellectual capacities

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

retardation (noun)	subnormality (noun)
the act of slowing down or falling behind	lack of normal development of intellectual capacities
a decrease in rate of change	the state of being less than normal (especially with respect to intelligence)
lack of normal development of intellectual capacities
any agent that retards or delays or hinders
the extent to which something is delayed or held back