Aperture width (labeled w in the below diagram) is the distance between two adjacent warp or weft wires, measured in the projected plane at the mid positions.

Warp: All wires running lengthwise of the cloth as woven.

Weft: All wires running across the cloth as woven.

Wire diameter (d) is the width of the wires in the woven cloth. (The wire diameter may be altered slightly during the weaving process.)

Pitch (p) is the distance between the midpoints of two adjacent wires. Represents the sum of the aperture width (w) and wire diameter (d).