Here's why:
* Origin: The word comes from the Middle English "apothecarie," derived from the Old French "apoticaire," which itself comes from the Greek "apothēkē," meaning "storehouse."
* Structure: The word is a single root word, with no clear additions at the beginning or end.
It's possible to *consider* "apo-" as a prefix, but it's more accurate to say that "apo-" is a part of the root word itself, derived from the Greek "apothēkē."