Trinomial nomenclature

In biology, trinomial nomenclature is used to name living things at a rank lower than species. The term trinomial nomenclature means "three-part name" or "system of three-part names".

If living things are divided into more categories than species such as a sub species then it gets a three part scientific name. The first part indicates the genus, the second part indicates the species, and the third part is particular to the living thing (at whatever rank it has been assigned). Trinomial nomenclature is similar to binomial nomenclature but the difference between both is that in binomial nomenclature the name of an organism is divided into two parts i.e. genus and species, and in trinomial nomenclature, the name of the organism is divided into three parts: genus, species and subspecies. "Genus": According to trinomial nomenclature, the first letter of the genera of an organism is denoted by a capital letter, comes before species, and is written in italics or underlined. "Species": According to trinomial nomenclature, the first letter of a species starts with a small letter and comes after the name of the genus of an organism. Subspecies: According to trinomial nomenclature, the first letter of a subspecies starts with a small letter and comes after the name of the species of an organism. For example, Brassica oleracea capitata in which Brassica represents genus name, oleracea represents species name and capitata represents subspecies name. The third name In trinomial nomenclature is subspecies. Eg:

  Homo sapiens sapiens--> mordern man. The third word stands for the subspecies 
   Puccinia graminis tritici--> Rust fungus. Third word stands for the pathogenic variety