retardation vs amentia

retardation and amentia both are nouns.

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

As nouns, amentia is a hyponym of retardation; that is, amentia is a word with a more specific, narrower meaning than retardation:

retardation (noun)	amentia (noun)
the act of slowing down or falling behind	extreme mental retardation
a decrease in rate of change
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