What prefix means "each" or "every"?

The prefix that means "each" or "every" is actually "uni-," which is not one of the provided choices. However, the closest correct answer given the options is "mono-," which means "one" or "single." This prefix is often used in medical terminology to denote singular entities, such as in the term "monocyte," which refers to a type of white blood cell that is single in nature. While "mono-" implies a focus on one, the concept of "each" or "every" can sometimes be understood in terms of individual units, and "mono-" can reflect this notion in specific contexts.

The other prefixes do not accurately convey the meaning of "each" or "every." "Multi-" refers to "many," indicating a plural quantity, while "tri-" denotes "three." As a result, when looking for a prefix that relates to the idea of singularity as a stand-in for "each" or "every," "mono-" is the most applicable choice among the options given.