The solid residue left after something has burned, usually wood and plant material (such as tobacco). It consists mainly of carbonates and bicarbonates of metals in the original organic material - the metals that primarily compose the ash of the analytical chemistry meaning.
In analytical chemistry, ash is one of the components in the proximate analysis of biological materials.
This is a disambiguation page — a navigational aid which lists other pages that might otherwise share the same title. If an article link referred you here, you might want to go back and fix it to point directly to the intended page.