主しゅ要よう因いんMeaningsNoun1. primary factor; main causeKanji used主(one's) master要needed因causeComposed of主しゅ要ようchief; main; principal; majorNa-adjective因いんcause; factor; hetu (direct cause, esp. as opposed to indirect conditions); the basis of one's argument (in hetuvidya)NounExamples1勤きん勉べんさが彼かれの素す晴ばらしい昇しょう進しんの主しゅ要よう因いんだった。Diligence was the principal factor in his remarkable promotion.