Which root word means "breast" in medical terminology?

In medical terminology, the root word "mast-" specifically refers to the breast. This term is derived from the Greek word "mastos" which also means breast. It is commonly used in various medical fields, particularly in gynecology and oncology, to refer to conditions related to the breast, such as mastitis (inflammation of the breast) and mastectomy (surgical removal of the breast).

The other root words provided do not relate to breast anatomy. "Adip-" pertains to fat, often used in terms like adipose tissue. "Chol-" relates to bile or cholesterol, frequently seen in discussions about liver function and bile production. "Cardio-" refers to the heart, as seen in terms like cardiovascular or cardiology. Thus, the correct option is clearly "mast-", as it is the only term among the choices that signifies the breast specifically.