a system of classification based on the variations in the patterns of the ridges, which are grouped into arches, loops, and whorls (A.L.W. or arch-loop-whorl system). "Arches are formed when the ridges run from one side to the other of the bulb of the digit, without making any backward turn, but no twist; whorls, when there is a turn through at least one complete circle; they are also considered to include all duplex spirals." The abbreviations used in making a record of fingerprints are:
a, arch;
l, loop;
w, whorl;
i, loop with an inner (thumb side) slope;
o, loop with an outer (little-finger side) slope. The ten digits are registered in four groups as follows, distinguished by capital letters:
A, the fore, middle, and ring fingers of the right hand;
B, the fore, middle, and ring fingers of the left hand;
C, the thumb and little finger of the right hand;
D, the thumb and little finger of the left hand.
See also:
dermatoglyphics.