What is the term for trimming the layers of the seam allowance to different widths?

The correct term for trimming the layers of the seam allowance to different widths is grading. Grading is a technique used in sewing to reduce bulk in seams, especially at curves and in areas where multiple layers of fabric come together. By trimming the seam allowance to various widths, it allows for a smoother lay of the fabric without excess thickness, which can cause ridges or puckering on the outside of the garment. Grading enhances the final appearance and ensures that the garment maintains a neat and professional finish.

Gradation, while similar in name, does not specifically refer to seam allowance trimming in sewing terms, but rather can refer to a gradual change in the size or color in a design context. Layering typically describes the technique of using multiple pieces of fabric or garments arranged atop one another, and shaping pertains to the manipulation of fabric to achieve desired contours or fitting in a garment.