Dictionary / Vocabulary / 秘伝
ひでん
secret (recipe, medicine, etc.); mysteries (e.g. of an art)
内弟子とは師と寝食をともにし、あらゆる武術のノウハウと秘伝を伝える制度だ。
Apprenticeship is a system where you eat, sleep and live with your master and are taught various martial arts know-how and secrets.