Fingerprint

A fingerprint with ink on a piece of paper

A fingerprint is a trace of a human finger left on a surface. Human fingers have small structures on them (like mountains and valleys). These structures are unique in every human; they can be used as means of identification, verification, and authentication.

Fingerprints are primarily categorized into three main types based on their ridge patterns:^[1]

Loops: Representing about 60-65% of fingerprints, loops curve inward or outward, making them relatively straightforward for identification purposes.
Whorls: Characterized by one or more circular ridges, whorls are complex but powerful for identification in specific scenarios.
Arches: The rarest type, featuring a ridge that curves and connects at the bottom, arches are challenging to identify accurately.

Sub-types provide further differentiation:

Radial and Ulnar Loops: Named for their distinctive shapes, these are crucial in forensics.
Central Pocket Loop, Double Loop, and Accidental Whorl: Unique patterns used for detailed fingerprint analysis.
Plain Whorl and Tented Arch: Additional forms that assist in secondary identification processes.

Besides these patterns, fingerprints include unique features like ridge density and special patterns (e.g., spirals) that enhance identification. These classifications and features underscore the complexity and utility of fingerprints in various applications, from forensic science to everyday security measures.

There are many different ways to take fingerprints. Forensic scientists use these techniques to identify a person.

Electronic fingerprint scanners became widespread in the early 21st century.

Fingerprint Media

Vingerafdruk.
The friction ridges on a finger
A non-tented fingerprint arch
Picture of a right loop fingerprint pattern. The bell shaped portion of the loop is leaning medially toward the body.*Image source: NIST.
Picture of a whorl fingerprint pattern
A tented arch fingerprint pattern.
A fingerprint created by the friction ridge structure
Exemplar prints on paper using ink
Barely visible latent prints on a knife
Fingerprint scanner identification on a Government building in Brazil.