Dear Martha and Grant,
A word representing the other half of a relationship with a mentor is “disciple.” My partner is an adherent of a sect of Buddhism in which this term is used commonly, as in “the oneness of mentor and disciple.” And the word has a very long history in English!
As a professional editor, I have delighted in your show for many years.
Protege also works.
ProtÃ©gÃ© (protÃ©gÃ©e if female) is exactly the right word. Interestingly, when Grant offered this suggestion, the caller believed that that word somehow implies superior performance. It doesn’t. You can be an utter failure as a protÃ©gÃ©. Yet many people seem to think that “protÃ©gÃ©” carries this connotation. A professor I had many years ago in college called this phenomenon “semantic interference.” Occasionally, one will see the words “protÃ©gÃ©” and “prodigy” confused, as in:
“He was a child protÃ©gÃ©. He could play Rachmaninov’s Piano Concerto #3 at the age of nine.”
That kind of usage is an eggcorn: the unintentional substitution of a similar-sounding word for the intended word. Semantic interference is similar to an eggcorn, but at the connotative rather than the denotative level of meaning. In such a case, the user employs the correct term, but the precise understanding of the term is adulterated by connotation that the user is transferring from a similar-sounding word, in this case, “prodigy.”