retard vs retardation

retard and retardation both are nouns.

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

retard (noun)	retardation (noun)
a person of subnormal intelligence	the act of slowing down or falling behind
	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

retard (verb)	retardation (verb)
lose velocity; move more slowly
cause to move more slowly or operate at a slower rate
slow the growth or development of
be delayed