At the core of Leisurology lies the fundamental concept of “leisure”, which serves as the primary object of Leisurology, the basis of theory, and the foundation for practical applications.This paper proposes eight basic categories that encapsulate the essence of leisure: authenticity, existence, embodiment, temporality and spatiality, difference, value, publicness, and futurity. These categories are closely related to the concept of “leisure”and can reveal its main content and characteristics. They can accommodate the basic contents of Leisurology and carry its whole theoretical system. Exploring the meanings of these categories and their relevance to leisure studies from the perspective of Philosophy, mainly Phenomenology, is of great significance for constructing a theoretical system of Leisurology with original and distinctive categories.