kerf

1. A groove or notch made by a cutting tool, such as a saw or an ax.
2. The width of a groove made by a cutting tool.

[Middle English, from Old English cyrf, a cutting.]

1. In a suspended acoustical ceiling, a groove cut into the edges of an acoustical tile to receive splines or supporting members of the ceiling suspension system.
2. A slot or cut made in a material such as wood or metal.