refers to "The Three Types of Learning" or "sangaku" which are considered to be three essentials in Buddhist practices. "Kai" refers to precept or "kairitsu", whereby one can learn good and prevent evil. "Jo" refers to meditative cultivation of spirituality or "zenjo", whereby one learns how to achieve mental concentration. "E" refers to wisdom or prajna or "chie", whereby one perceives the truth and achieves enlightenment.

is used for disciplining monks' way of life. "Kai" refers to one's mental action to voluntarily observe discipline and "Ritsu" refers to heteromous discipline.

is meditation, whereby one learns to quiet his or her mind and focus on one single object.

is one's ability to perceive the reason and logic of things (=insight) and to treat them in the proper way. In Heart Sutra, it is commonly spelt as "prajna" rather than "wisdom" (Note: "wisdom" and "prajna" are synonyms in Japanese), which is one's mental action to clarify the truth and attain enlightenment.