A gore is a fabric envelope section between two vertical seams in a hot-air balloon.
Balloon envelopes are assembled from many long, curved fabric panels. Each panel is called a gore, and the gores are sewn together to create the rounded shape that holds the heated air. Their carefully calculated curves allow a flat collection of fabric pieces to form a three-dimensional envelope.
The seams between gores also help distribute loads through the envelope. Additional vertical and horizontal reinforcing tapes may be sewn over or alongside the fabric, especially in areas exposed to stress during inflation and flight.
Gore is often confused with panel. In some descriptions, “panel” is used informally for a fabric piece, but gore is the standard ballooning term for the long envelope segment extending from the mouth toward the crown. The basket and burner are separate components.