gusset

right|thumb|upright|Late medieval shirt with gussets in the seams at shoulder, underarm, and hem. From a copy of the [[Tacuinum Sanitatis, 14th century.]]

In sewing, a gusset is a triangular or rhomboidal piece of fabric inserted into a seam to add breadth or reduce stress from tight-fitting clothing. Gussets were used at the shoulders, underarms, and hems of traditional shirts and chemises made of rectangular lengths of linen to shape the garments to the body.