Final answer:
The combining form meaning 'disease' is path/o, commonly used in terms like pathology, which is the study of diseases.
Step-by-step explanation:
The combining form meaning "disease" is path/o. This form can be found in various medical terms related to diseases, such as pathology, which is the study of the causes and effects of diseases. Medical terminology often uses Greek and Latin roots to form the basis of terms for conditions and procedures, with combining forms used to link different word parts together.