Here's why:
* "De" is a prefix that often means "away from," "down from," or "reverse of." For example, "depart" (to go away from), "decompose" (to break down), and "deconstruct" (to take apart).
* "Detail" is a noun meaning a small part or feature of something. It has a separate etymology, coming from the Old French word "detail."
Therefore, "de" is not a prefix in "detail" because it's not a separate part of the word with its own meaning. The entire word "detail" has a single, distinct meaning.