Within the International Nath Order, an Adept is one who has attained to the sphere of Siddhi.
Siddha is the Sanskrit name for that person. Adept is the English word the Order uses. It is not a grade conferred by initiation. An initiate has received the transmission. An Adept has attained. Mahasiddha is the great adept of the older lists. This page only names the INO word.