Rough opening
The bare framed hole in the wall — studs and header, no window — that a window is built to fit into, slightly larger than the unit so it can be shimmed and sealed.
What it means for you
A replacement window is ordered a bit smaller than the opening on purpose; that gap is expected and gets shimmed, insulated, and sealed. Going “back to the rough opening” is exactly what makes a full-frame job cost more than an insert — and what lets the installer fix rot and re-flash.
Where you'll see it
In measuring and in the full-frame-vs-insert decision.
Related terms
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