fingerprint pattern type

   Formed by a series of lines, corresponding to ridges (hills) and grooves (valleys) on the skin of the fingertip.

   There are eight basic types of fingerprint patterns:

   1. plain arch: the simplest pattern. The ridges enter on one side, rise to form a wave in the center, and exit smoothly on the opposite side.

   2. tented arch: variation of the plain arch. Ridges at the center are thrust upward in a more abrupt manner similar to the appearance of a tent pole.

   3. radial loop: a pattern in which one or more ridges enter on the side toward the thumb (the side on which the radius bone of the forearm lies), recurve, and then exit on the same side.

   4. ulnar loop: a pattern in which one or more ridges enter on the side toward the little finger (the side on which the ulna bone of the forearm lies), recurve, and then exit toward the same side.

   5. plain whorl: a pattern in which one or more ridges form a complete revolution around the center. Whorls generally have two or more deltas.

   6. central pocket loop: a variation of the plain whorl pattern. Some ridges tend to form a loop pattern, which recurves and surrounds a whorl at the center.

   7. double loop (twinned loop): another type of whorl.

   In it two separate loop formations are present and may surround each other.

   8. accidental: a relatively rare type of pattern, having three or more deltas, or having all the characteristics of two or more different pattern types (excluding the plainarch).

   This category is used to accommodate those patterns that do not conform to any of the patterns previously described.