對顯教而言，謂大日如來所說之金胎兩部教法也。是為法身佛內證之境界。深密秘奧，故云密教，又為對未灌頂人不許顯示之教法，故云密教。二教論上曰：「法佛談話，謂之密藏，言秘奧實說。」又曰：「自性受用佛，自受法樂故，與自眷屬各說三密門，謂之密教。」日本東密於此密教立事理二密。見理密條。
idem, also esoteric teaching in general; the two classes are divided into the密教 esoteric or Yoga school, and 顯教 the open schools or teaching, comprising all the sects of Buddhism, except the esoteric sect. The密教三藏 Tripiṭaka of the esoteic sect are, as its sutra, the 大毘盧舍那金剛頂經; as its vinaya, the 蘇婆呼經根本部; as itsśāstras, the 莊嚴菩提心經, etc., q.v.
法身佛大日如來所說的內證真言教法，因其文其義，秘密難曉，故稱密教。又因是對未灌頂的人不許顯示的教法，故稱密教。