In traditional Chinese culture, qi (more precisely qì, also chi, ch'i or ki) is an active principle forming part of any living thing. Qi is frequently translated as "natural energy", "life force", or "energy flow". Qi is the central underlying principle in traditional Chinese medicine and martial arts. The literal translation of "qi" is "breath", "air", or "gas".

Concepts similar to qi can be found in many cultures, for example, prana and cit in Hindu religion, mana in Hawaiian culture, lüng in Tibetan Buddhism, ruah in Hebrew culture, and Vital energy in Western philosophy. Some elements of qi can be understood in the term energy when used by writers and practitioners of various esoteric forms of spirituality and alternative medicine. Elements of the qi concept can also be found in Western popular culture, for example "The Force" in Star Wars. Notions in the West of energeia, élan vital, or "vitalism" are purported to be similar.

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