Which one of the following word parts means "to lead or pull"?

The word part that means "to lead or pull" is -ductor. This suffix derives from the Latin root "ducere," which translates to lead. In medical terminology, it is commonly found in words such as "conductor," which refers to something that leads or guides, and "reductor," which implies leading something back. The presence of -ductor indicates a function of leading or pulling within a broader context, particularly in anatomical terms.

The other options do not convey the meaning of leading or pulling. "An-" is a prefix indicating negation or absence, "semi-" means half or partially, and "-ptsosis" refers to a condition of falling or drooping. Understanding the meanings of these word parts is essential in deciphering medical terminology, as it helps in identifying the functions and relationships between different components of medical words.