In the context of Buddhist philosophy, one way to describe experience in terms of eighteen elements (eye, form, and eye consciousness; ear, sound, and ear consciousness; nose, smell, and nose consciousness; tongue, taste, and tongue consciousness; body, touch, and body consciousness; and mind, mental phenomena, and mind consciousness).
This also refers to the elements of the world, which can be enumerated as four, five, or six. The four elements are earth, water, fire, and air. A fifth, space, is often added, and the sixth is consciousness.