Axe, an instrument used for hewing timber and chopping wood, and (till the introduction of firearms) as a weapon. The modern axe consists of a head of iron edged with steel, and a helve or handle. Stone axes, however, are amongst the earliest of human inventions, and are often used by savage tribes. They differ from celts (chisels) in being of more complex shape and fitted for hewing. The modern axe differs from the adze in that its head is fixed in the plane of the sweep of the handle, whereas the head of the adze is fixed transversely to this plane.