Which prefix is most closely associated with speed?

The prefix "tachy-" is rooted in the Greek word "tachys," which means swift or fast. It is often used in scientific and medical terms to denote speed, especially in contexts like tachycardia, which refers to an elevated heart rate. This prefix is specifically designed to convey the idea of rapid movement or fast processes, making it the most closely associated with speed among the given choices.

Other prefixes, while they may imply varying degrees of intensity or an overarching quality, do not carry the specific connotation of speed that "tachy-" does. For instance, "super-" generally suggests superiority or excess, "ultra-" implies something beyond or extreme, and "trans-" suggests crossing or going beyond, none of which directly relate to the concept of speed in the way "tachy-" does.