What does the medical terminology combining form -ion mean?

-ion means process or act of in medical terminology, as in other Word formations. So the process of digesting is digestion, the act of respiring is respiration, and whe we masticate, the act is mastication.
The Word part -ion in medical terms means "craniometric point" as in gonion or a body point as in acromion. In common terms it can mean "condition of, result of, act of, process of, state of".
The abbreviation ion stands for several things. One of the things it stands for is Inferior Esophageal Nerve. Another item that ion stands for is Ionic Self-Diffusion Coefficient D.