Final answer:
The term 'posterior' is used to describe something that is pertaining to the back in medical terminology, rather than a term ending with the suffix '-ior.'
Step-by-step explanation:
The medical term for 'pertaining to the back' using the suffix '-ior' is not commonly used. Instead, the term posterior is generally used to describe the back or direction toward the back of the body. There isn't a standard anatomical term ending with '-ior' that refers to the back, but 'posterior' is the appropriate term. In anatomical terminology, 'posterior' (or dorsal) indicates a position towards the back side of the body. For example, in human anatomy, we would say that the popliteus muscle is posterior to the patella, meaning it is located towards the back relative to the patella (the kneecap).