Qi 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 tiān 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, especially in Asia.