Which prefix signifies "large"?

The prefix that signifies "large" is "macro." This prefix is commonly used in various fields, including medicine, biology, and technology, to indicate something that is large in scale or size. For instance, in medical terminology, "macrophage" refers to a type of large white blood cell that engulfs and digests cellular debris and pathogens.

In contrast, "tri" denotes the number three, "retro" relates to something being backward or earlier, and "infra" means beneath or below, indicating that these prefixes do not convey the meaning of largeness.