Which prefix refers to being "under" in terms of position?

The prefix that refers to being "under" in terms of position is "infra-." This prefix is derived from Latin, where it means "below" or "beneath." It is commonly used in various scientific and medical terminologies to denote a position lower than or beneath a particular structure or point of reference. For example, in anatomy, the term "infrastructure" refers to the underlying framework or supportive structures that are situated beneath the primary elements.

While there are other prefixes that can imply different aspects of position—such as "hypo-" which means "below normal" in a different context, "exo-" which refers to things that are "outside" or "external," and "endo-" which denotes "within" or "inside"—none of these convey the specific positional meaning of being directly "under." Thus, "infra-" is the most accurate choice for this particular question regarding positional references.