Fingerprint swirl, also known as a WHORL, is an arrangement of ridges on the surface of a finger that forms a circular pattern. It is one of the three basic fingerprint patterns used for identification purposes. Fingerprint swirls are characterized by ridges that form a circular pattern, with two or more deltas (triangular-shaped ridges) located at the center. They are the second most common type of fingerprint pattern, after the loop pattern.