, also commonly spelled ch'i, chi or ki, is a fundamental concept of everyday Chinese culture, most often defined as "air" or "breath" (for example, the colloquial Mandarin Chinese term for "weather" is tian qi, or the "breath of heaven") and, by extension, "life force" or "spiritual energy" that is part of everything that exists. References to qi or similar philosophical concepts as a type of metaphysical energy that sustains living beings are used in many belief systems.
This article provides a brief introduction to the the history and theory of acupuncture, including a traditional Chinese medical view, as well as an easily-understood explanation for the layman.