The use of the word "mentor" in English to mean an "advisor" dates to the 18th century. Nowadays you can also hear the word "mentee," which is formed as if "mentor" were a Latin verb, but that is a bit of linguistic nonsense that does not fit the Greek origins of the word at all! The word "mentee" was coined in the 1960s. To fit the Greek, it would be better to talk about a "mentor" and a "telemachus," rather than mentor and mentee. :-)
You can read more about Greek Mentor at Wikipedia, which is also the source for this picture of Mentor with Telemachus:
