Enclosure or Sunroom?

Enclosures are often referred to as "sunrooms" -- and vice versa. Is it mere semantics?

Maybe, but as a general rule, the ceilings and walls of some permanent enclosures can be opened manually or via motorized systems; with sunrooms, ceilings and walls are normally fixed. And traditionally, sunrooms are built as a covered-and-windowed porch or three-season room, whereas enclosures are specifically built with a pool or spa in mind.