Disciple:
"One who accepts and assists in spreading the doctrines of another: as a: one of the twelve in the inner circle of Christ's followers according to the Gospel accounts b: a convinced adherent of a school or individual" Webster Dictonary
In Luke 6:40, Jesus invites us to be like him and in Mat 28:19, Jesus commands us to "make disciples" of all nations. He did not tell us to only make only believers, but He said disciples. The Greek word, "matheturo" (teaching and instructing) used in the verse is more of a process than an event. As we note the example of Jesus, we notice not only teaching scriptural and spiritual knowledge of God but the practical living of that knowledge.
Mentor:
"a: a trusted counselor or guide b: tutor, coach" Webster Dictonary
Of course, Jesus and Barnabas exemplify the role of a Mentor. They modeled servant mentality and servanthood as both combined the roles of teaching and being a role model. Mentoring is not so concerned about a curriculum but being the example to emulate as life's lessons or skills are passed on to the protegee.