Derived from the Greek word cteno, meaning "comb", the ctenoid fish scale name refers to comb-like ctenii, which decorate the edges of the scale, as illustrated in the MIC-D digital image presented below. The spiny posterior margin of ctenoid scales has a wide variety of morphologies.

View a second image of the ctenoid scale.

These scales are commonly found in the majority of bony fishes (referred to as the Teleostei), and the anterior (or front) part of each scale is usually tucked underneath the rear portion of the preceding scale. As the fish grows, so do the scales, resulting in a pattern of concentric growth "rings" that increase in number with the scale size and appear similar to those found in the cross section of tree trunks. In some cases, ctenoid scale growth patterns are utilized to determine the age of a fish.

Ctenoid scales are composed of two main regions, a surface layer having a hard shell resulting from crystallized calcium salts, and a deeper layer that is built with collagen-type fibrils. Three generalized types of ctenoid scales have been categorized. They include crenate scales having simple indentations on the edges, spinoid scales that are clustered with a network of spines attached to the main scale body, and ctenoid scales that display ctenii formed as separate bony growths, which are distinct from the scale's main body.