Glossary
Sloper
A sloper is a basic pattern fitted to a body or a size chart with no seam allowance, no style lines and no ease beyond what the body needs to move.
It is the thing you draft once and then never cut a garment from directly. Every style you make afterwards is traced from it and changed — a dart moved, a seam added, fullness released — which is why an error in the sloper repeats in everything built on it.
In British usage the same piece is usually called a block. The two words mean the same thing, and which one a workroom uses tells you roughly where it learned to draft.
A sloper has no seam allowance because allowance is a property of the garment you are cutting, not of the shape you are developing. Adding it too early is one of the most common reasons a first pattern comes out large.