Which of the following prefixes means "not"?

The prefix "non-" is specifically used to indicate negation or absence. It universally conveys the meaning of "not" when attached to the root of a word. For instance, in the term "nonexistent," it clearly signifies something that does not exist. This prefix is a straightforward way to alter the meaning of a word to express negation, making it widely applicable in medical terminology and beyond.

In contrast, the other prefixes serve different purposes. "Poly-" means many or much, "peri-" refers to around or surrounding, and "primi-" denotes the first or primary. Each of these prefixes adds distinct meanings that do not imply negation, thereby distinguishing "non-" as the sole prefix that directly translates to "not."