For ancient Chinese, Qi was the unseen force that permeated everything. Qi is the dynamic, subtle function of all that exists...everything and everyone has Qi. It may be hard for the modern Western minds to grasp that the ancient Chinese did not emphasise on precise, clear definitions.
Rather, Qi was an almightily tool to help explain life in its broadest context. At the same time, Qi could be used very precisely and clearly in given the right context. Qi in ancient China could be used in science, medicine, weather, philosophy, arts, cooking and practical daily life.