Trinomi(n)al nomenclature
The system of applying a scientific name to a subspecies, involving the use of a third name added to those given to the genus and species under the rules of binomial nomenclature. The 'subspecific name', like the 'specific name', always has a small initial letter. One subspecies under each species has a subspecific name identical to the specific name, this being known as the 'nominate' subspecies. For example, in the case of the Blue Tit Parus caeruleus the nominate species is the continental one, with the name P.c. caeruleus, while the one breeding in the British Isles is name P.c. obscurus.From Peter Weaver's Birdwatcher's Dictionary
Copyright © 1981 by Peter Weaver