agent vs repressor

agent and repressor both are nouns.

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

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

agent (noun)	repressor (noun)
the semantic role of the animate entity that instigates or causes the happening denoted by the verb in the clause	an agent that represses
an active and efficient cause; capable of producing a certain effect
a businessman who buys or sells for another in exchange for a commission
a representative who acts on behalf of other persons or organizations
any agent or representative of a federal agency or bureau
a substance that exerts some force or effect