Qi

In traditional Chinese culture, qi is a principle that operates inside all living beings.

It is often appealed to as an explanation for a variety of effects in alternative medicine including acupuncture, martial arts, feng shui, and is a part of the religious and philosophical ideas of Taoism.

It is often translated to mean "energy flow" and to explain qi in a Western context, reference is often made to the vitalist concept of élan vital.

Many people deny qi on scientific grounds( or see it as a metaphor rather than a real force): pointing to the better explanations given by science for the effects that qi is supposed to bring about. In martial arts, those who have Westernized and secularised the martial arts point to the physical laws of motion and the scientific understanding of physiology and psychology as a better explanation of the techniques taught by martial artists. Scientific studies of acupuncture shows that you can get the effect that acupuncture claims is done by insertion of acupuncture needles along qi-based meridian lines by random insertion of needles (as well as use of retracting "fake needles"). With feng shui, you can hire numerous feng shui consultants who claim to be able to tap into the power of qi, only for them to produce different recommendations.

Romanization
There are a variety of ways to Romanize Chinese words and characters: qi is the correct spelling in pinyin, which is the Romanization scheme approved by the Chinese government and used by most western scholars today. "Ch'i" (note apostrophe) is the correct spelling in the Wade-Giles system, which was widely used before pinyin, survives in many older texts, and is still used by some western scholars today.

The Japanese name for the same concept is ki, and the Korean name is gi.