氣 (qi, chi, ki) is a polysemous word, generally referring to a circulating life force whose existence and properties are the basis of much Chinese philosophy and medicine.
氣 (qi, ki, chi) as defined in the Oxford Dictionary, is the circulating life force whose existence and properties are the basis of much Chinese philosophy and medicine. Wikipedia has a longer definition, pointing out a couple of dozen potential meanings.
氣 is a purely hypothetical concept with neither grounding in current scientific theories nor basis in evidence based experimentation. For example, see the Sceptic's dictionary entry.
