Three Realms  三界

   Sanskrit word is Trailokya. It is Buddhist metaphysical equivalence for the triple world of earth, atmosphere and heaven.

   1.Realm of Sensusous Desire (Sanskrit word is Kamadhatu) of sex and food. It includes the Six Hevens of Desire, the Human World and the Hells.

   2.Realm of Form (Sanskrit word is Rupaadhatu) of matter which is substantial and resistant. It includes the Heavens of Four Zen (Sanskrit word is Brahmalokas).

   3.Realm of Formlessness (Sanskrit word is Arupadhatu) of pure spirit, where there are no bodies and matters to which human terms would apply, but where the mind dwells in mystic contemplation; its extent is indefinable, but it is conceived of in Four Stages/Places of Emptiness in the immaterial world.

   三界又可總分為有情界（有情識的生物）和器世界（處所）兩類，而以有情界為主體。三界是據有情所造善、惡業及修不同定業所感苦、樂、色、無色等不同果報而建立的。界，限也、別也。謂三界分限各別不同。

   (一)、欲界，　即地獄、餓鬼、畜生、阿修羅、人間及六欲天之總稱。欲有四種：一者情欲，二者色欲，三者食欲，四者婬欲。下極阿鼻地獄，上至第六他化天，男女相參，多諸染欲，故名欲界。（六欲天者，四天王天、忉利天、夜摩天、兜率天、樂變化天、他化自在天。）

   (二)、色界，色即色質，謂雖離欲界穢惡之色，而有清淨之色，始從初禪梵天，終至色究竟天，凡有一十八天，並無女形，亦無欲染，皆是化生，尚有色質，故名色界。（一十八天者，梵眾天、梵輔天、大梵天、少光天、無量光天、光音天、少淨天、無量淨天、遍淨天、無雲天、福生天、廣果天、無想天、無煩天、無熱天、善見天、善現天、色究竟天。）