Binomial Nomenclature - Writing Binomial Names

Writing Binomial Names

By tradition, the binomial names of species are usually typeset in italics; for example, Homo sapiens. Generally the binomial should be printed in a font different from that used in the normal text; for example, "Several more Homo sapiens fossils were discovered." When handwritten, each part of a binomial name should be underlined; for example, Homo sapiens.

The first part of the binomial, the genus name, is always written with an initial capital letter. In current usage, the second part is never written with an initial capital. Older sources, particularly botanical works published before the 1950s, use a different convention. If the second part of the name is derived from a proper noun, e.g. the name of a person or place, a capital letter was used. Thus the modern form Berberis darwinii was written as Berberis Darwinii. A capital was also used when the name is formed by two nouns in apposition, e.g. Panthera Leo or Centaurea Cyanus.

When used with a common name, the scientific name often follows in parentheses, although this varies with publication. For example "The house sparrow (Passer domesticus) is decreasing in Europe."

The binomial name should generally be written in full. The exception to this is when several species from the same genus are being listed or discussed in the same paper or report, or the same species is mentioned repeatedly; in which case the genus is written in full when it is first used, but may then be abbreviated to an initial (and a period/full stop). For example, a list of members of the genus Canis might be written as "Canis lupus, C. aureus, C. simensis". In rare cases, this abbreviated form has spread to more general use; for example, the bacterium Escherichia coli is often referred to as just E. coli, and Tyrannosaurus rex is perhaps even better known simply as T. rex, these two both often appearing in this form in popular writing even where the full genus name has not already been given.

The abbreviation "sp." is used when the actual specific name cannot or need not be specified. The abbreviation "spp." (plural) indicates "several species". These abbreviations are not italicised (or underlined). For example: "Canis sp." means "an unspecified species of the genus Canis", while "Canis spp." means "two or more species of the genus Canis". (The abbreviations "sp." and "spp." can easily be confused with the abbreviations "ssp." (zoology) or "subsp." (botany), plurals "sspp." or "subspp.", referring to one or more subspecies. See trinomen (zoology) and infraspecific name (botany).)

The abbreviation "cf." is used when the identification is not confirmed. For example "Corvus cf. splendens" indicates "a bird similar to the house crow but not certainly identified as this species".

In some contexts the dagger symbol ("†") may be used before or after the binomial name to indicate that the species is extinct.