Because "Sensei" has different meanings in different countries that could possibly cause issues in the future, in supplementary material from 2016 onward, usage of the word has ceased, and been replaced by "master." Because of this, Wu is now "Master Wu." Officially, this extends to as "Sensei," but Garmadon is the only one who hadn't been referred to as "master" in the show until "The Hands of Time."