Which prefix means "under" or "below"?

The prefix that means "under" or "below" is "sub-." This prefix is derived from Latin, where "sub" translates to "under" or "beneath." It is commonly used in medical terminology to describe anatomical locations or conditions that are positioned below or underneath something else. For example, "subcutaneous" refers to the layer of tissue beneath the skin, indicating its location relative to the skin surface. Understanding prefixes like "sub-" is essential for accurately interpreting and constructing medical terms, as they give clear indications of location and relationship in the medical field.