agent (suomeksi)

agentti (s: one who acts in place of another / computing: part of the system that performs action on behalf of a client or server / grammar: performer of the action in a sentence)
toimija (s: one who exerts power / active power or cause)
asiamies (s: one who acts in place of another)
vaikuttaja (s: active power or cause)
vaikuttava aine (s: active power or cause / vaikuttava aine / medicine)
taudinaiheuttaja (s: active power or cause / vaikuttava ainetaudinaiheuttaja / pathology)