Final answer:
The medical term that combines the suffix '-al' with the meaning of 'pertaining to one side' is 'lateral', which is used to describe positions toward the side of the body.
Step-by-step explanation:
The medical term that uses the suffix -al to indicate 'pertaining to one side (only)' is lateral. In medical terminology, 'lateral' describes the side or direction toward the side of the body. For instance, the thumb is lateral to the other digits, meaning it is on the side closest to the body's outer part compared to the other fingers. The suffix -al is commonly added to the root of a medical term to denote the meaning 'pertaining to'.