Cosmos is an orderly or harmonious system. Cosmos originates from a Greek term meaning "order, ordely arrangement, ornaments". The word cosmetics originates from the same root.
Pythagoras is said to have been the first philosopher to apply the term cosmos to the universe, perhaps from application to the starry firmament. The term so used is parallel to the Zoroastrian term aša, the concept of a divine order, or divinely ordered creation.
In theology the term can be used to denote the created universe, not including God. The Septuagint uses both kosmos and oikumene for the inhabited world. In Christian theology, the word was also used synonymously with aion to refer to "worldly life, this world" as opposed to the afterlife. In philosophical use the word "absolute", cosmos and universe can be employed synonymously to include all that exists. In physical sense it is often used in a technical way, referring to a space-time continuum; see Physical cosmology.
cosmology refers to the study of the cosmos in several of the above meanings, depending on context.
The philosopher Ken Wilber uses the term kosmos to refer to all of manifest existence, including various realms of consciousness. The term kosmos so used distinguishes a nondual universe (which, on his view, includes both noetic and physical aspects) from the strictly physical universe that is the concern of the traditional sciences.
Author Patrizia Norelli-Bachelet presents a synthesis of the harmonies of the Cosmos, in her book The Gnostic Circle Therein, she writes that the Cosmos (or the Cosmic principle) should be seen in relation to the Transcendent and Individual principles of existence as well.