Rabbi/Rabboni

The same came to Jesus by night, and said unto him, Rabbi, we know that thou art a teacher come from God: for no man can do these miracles that thou doest, except God be with him. John 3:2
Jesus said unto her, Mary. She turned herself, and saith unto him, Rabboni; which is to say, Master. John 20:16
 
In modern society, rabbi is the official title of the leader of a Jewish congregation. It is similar to the title of reverend for a Protestant minister or father for a Catholic priest.
 
But in Jesus’ time, rabbi was a term of respect meaning “teacher” or “master”. In John 3:2, Nicodemus’s reference to Jesus as “rabbi” probably means “teacher”. Nicodemus wanted to learn more about this Jewish teacher and miracle worker who was impressing the crowds in the region of Galilee.
 
In John 20:16, Mary Magdalene’s recognition of Jesus as “Rabboini” pays homage to Him as her Master. After His resurrection, she recognized Him as such when He called her by name. Rabboni is the Aramaic form of Rabbi. Aramaic was the common language spoken in Israel during New Testament times.
 
Whether we call Jesus Rabbi or Rabboni, the meaning is the same: He is our Master Teacher and Guide, who deserves our utmost respect and loyalty.