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.