
Sensei (kanji: 先生, "born earlier") is a Japanese word of Chinese origin and is used in most cases to mean a teacher or other high-ranking professional of society (lawyers, accountants, clergymen, etc.).
It is also used for someone who makes or creates things, such as craftsmen or mangaka, that is held in high esteem by the speaker or society as a whole. In addition to being an honorific term of address, "-sensei" is also a naming suffix that replaces the usual address suffix "-san" in this context. For example, in Japanese, "Splinter-san" addresses Splinter as an ordinary person, while "Splinter-sensei" is the equivalent of "Master Splinter". In the Western world, the term is mostly thought of as a term to designate a martial arts teacher exclusively, likely due to the proliferation of martial arts films from the 1960s through the 1990s.
In TMNT[]
Being a franchise based on martial arts, although sometimes rather tenuously, sensei are plentiful in the Teenage Mutant Ninja Turtles franchise. The most well-known is the Ninja Turtles' sensei, Splinter. It is rare in TMNT stories for characters to address sensei characters in a suffixed manner (i.e., "Splinter-sensei"), but more common in Usagi Yojimbo stories including TMNT crossover stories. In these stories, Splinter's counterpart Kakera is not addressed as "Master Kakera," but as "Kakera-sensei".
IDW[]
In the IDW continuity's Teenage Mutant Ninja Turtles: The Secret History of the Foot Clan mini-series, the Shredder calls Dr. Patrick Miller "Miller-sensei" in issue 2. In the Teenage Mutant Ninja Turtles: Shredder in Hell mini-series, Kid calls Splinter "Yoshi-sensei" in issue 3.
Rise of the TMNT[]
In Rise of the Teenage Mutant Ninja Turtles, Splinter is rarely referred to as "sensei" by anybody despite being one as he decidedly has a more parental role than one of a teacher[1][2] and is unbothered by that lack of address in the series. In "Insane in the Mama Train", the Ninja Turtles call him "sensei" as part of their transformation into traditional Hamato Clan ninja, but it is to highlight how out of character they are being. After the Ninja Turtles realize the difficulty in pretending to be who they are not and Splinter concludes he should have just let them be themselves in "End Game", the Ninja Turtles stop addressing him as "sensei". Foot Recruit refers to Foot Lieutenant and Foot Brute as "sensei". Casey Jones II refers to future and present Leonardo alike as "sensei".