noun
Usage: usually capitalized G & 1st L
Etymology: after J. L. Gay-Lussac
1. : a statement in chemistry and physics: when two or more gaseous substances combine to form a gaseous compound the volume of the product is either equal to the sum of the volumes of the factors or is less than and bears a simple ratio to this sum — called also law of combining volumes ; compare avogadro's law
2. : charles's law