A.T. Robertson Commentary John 20:16

"Jesus saith unto her, Mary. She turneth herself, and saith unto him in Hebrew, Rabboni; which is to say, Teacher." — John 20:16 (ASV)

Mary (Μαριαμ). Aramaic form in Aleph B W, though Μαρια in 19:25. Clearly the old familiar tone of Jesus was in the pronunciation of her name.

Rabboni (Ραββουνε). Aramaic again for Διδασκαλε (Teacher), "my Teacher." In N.T. only here and Mr 10:51 though practically the same as Ραββ. See 11:28 for "the Teacher" (Rabbi). These two simple words tell the great fact that Christ is risen and Mary has seen him. One says little in really great moments.