What does the prefix "tachy-" mean?

The prefix "tachy-" originates from the Greek word "tachys," which means "swift" or "fast." In medical terminology, it is commonly used to denote something that occurs at an increased or rapid rate, particularly in reference to heart rates, such as in the term "tachycardia," which refers to a faster than normal heart rate. This prefix indicates speed, making it the correct choice in this context.

The other options do not align with the meaning of "tachy-." For instance, "slow" would contradict the idea of speed, and "normal" does not imply any particular pace. "Excessive" also suggests a level beyond the normal range but does not specifically indicate speed, as "tachy-" does.