Jing, essence, also called kidney essence or essence of life, is a fundamental substance constituting the body and maintaining the life activities. Stored in the kidney, it is the material basis for all kinds of functional activities and is also responsible for human growth, development and reproduction. The essence stored in the kidney is comprised of congenital jing (also called congenital essence) and acquired jing (also called acquired essence), belongs to kidney yin.

精或腎精藏於腎，是構成和維持人體生命活動的基本物質。腎精是生命之根本，又是人體生命力的功能表現。腎精促進人體的生長、發育、生殖，並滋養所有臟腑。腎藏之精包括先天之精和後天之精，屬腎陰。