fingerprint

A fingerprint is an impression made by the unique arrangement of friction ridges on the skin of the fingertips and thumbs. The patterns of these ridges are formed by the skin’s outer layer and are associated with sweat pores, producing a distinctive map that remains stable over a person’s lifetime. Fingerprints have long been used for identification in forensic contexts and increasingly as a biometric security measure.

Friction ridges create three broad pattern classes: arches, loops, and whorls. Arches rise and bend forward, with plain arches and tented arches as subtypes. Loops enter from one side, recur to the same side, and exit; they are further categorized as radial or ulnar based on the direction of the loop. Whorls are more complex and include plain whorls, central pocket loops, double loops, and accidental patterns. Within these patterns, individual ridge characteristics, or minutiae—such as ridge endings, bifurcations, and short ridges—are used to distinguish one print from another.

The patterns are generally considered highly unique and are typically permanent, remaining unchanged except for damage from scarring or severe injury. While extremely rare, there is no absolute guarantee of uniqueness across all individuals, and even high-quality prints can be difficult to match if partial or distorted.

In practice, fingerprints are collected as latent prints from surfaces or as live-scan digital images. They are analyzed and matched against databases using automated systems that rely on minutiae and pattern classification. Applications span criminal identification, security and access control, and personal devices that use fingerprint recognition for authentication. Limitations include variable print quality, partial prints, and environmental factors that can affect collection and matching.