dampen vs retard

dampen is not a noun while retard is a noun.

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

As verbs, retard is a hypernym of dampen; that is, retard is a word with a broader meaning than dampen:

Other hypernyms of dampen include check, delay.

dampen (noun)	retard (noun)
	a person of subnormal intelligence

dampen (verb)	retard (verb)
lessen in force or effect	lose velocity; move more slowly
make moist	cause to move more slowly or operate at a slower rate
check; keep in check (a fire)	slow the growth or development of
make vague or obscure or make (an image) less visible	be delayed
reduce the amplitude (of oscillations or waves)
suppress or constrain so as to lessen in intensity
deaden (a sound or noise), especially by wrapping