Q.When members of any species have large variations then ________ system is used.

Trinomial nomenclature (from the Latin tri, meaning three) extends ordinary binomial nomenclature by adding a third name, giving trinomen: a generic name, a species name, and a subspecies name. This naming system was proposed by Thomas Henry Huxley and Hugh Edwin Strickland to handle cases where a single species shows enough internal variation across its geographic range or populations that it makes sense to formally recognise distinct subspecies within it.

Trinomial names are used specifically when members of a species display large enough dissimilarities that the species can be meaningfully subdivided into subspecies, based on those observed differences. Structurally, a trinomial name is simply an extension of the binomial system with a subspecies name appended as the third word; formatting-wise, all three names are set in italics, but only the first (generic) name is capitalised, and if the name is handwritten it should be underlined separately rather than italicised. …