Here's a breakdown:
* Jōnin (上忍) is the Japanese word for "senior ninja" or "master ninja."
* Jonin is a casual pronunciation often used in the English dub of the anime.
Jonin are highly skilled and experienced ninjas who have proven themselves through their abilities and service to their village. They are often entrusted with leadership roles, training younger ninjas, and carrying out important missions.
In the context of the show, "jonin" is a term of respect and signifies a high level of ninja mastery.