surrogate
n. countablen. a person or thing that takes the place of someone or something else. You use this when one person acts for another, especially in a formal or legal way.
n. a person or thing acting as a substitute for another. Often carries a formal or technical nuance, implying a functional equivalence in a specific role or context.
The vice president acted as a surrogate for the president during the meeting.
Since the CEO could not attend the international summit, she sent a trusted surrogate to negotiate on her behalf.
In psychological research, researchers sometimes use a surrogate measure when the primary outcome is too difficult or unethical to observe directly over a long period.
From Latin surrogātus, perfect passive participle of surrogō (“ask”); a variant of subrogō, from sub (“under”) + rogō (“ask”).
Often used with the preposition 'for' to indicate the person or thing being replaced.