agent vs retardation

agent and retardation both are nouns.

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

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

agent (noun)	retardation (noun)
the semantic role of the animate entity that instigates or causes the happening denoted by the verb in the clause	the act of slowing down or falling behind
an active and efficient cause; capable of producing a certain effect	a decrease in rate of change
a businessman who buys or sells for another in exchange for a commission	lack of normal development of intellectual capacities
a representative who acts on behalf of other persons or organizations	any agent that retards or delays or hinders
any agent or representative of a federal agency or bureau	the extent to which something is delayed or held back
a substance that exerts some force or effect