Skip to content

The Name Game: What Is Binomial Nomenclature?

Magpie

When we see the common names for plants and animals written down, they are often accompanied by a two-part Latin-looking name in italics. This is called binomial nomenclature. But what is this, and why do we need it when we already have names in English?

A Brief History of Binomial Nomenclature

Scientists and thinkers have long understood that to make sense of the natural world’s complexity, we need to classify organisms, a science known as taxonomy. By grouping similar creatures and plants together, they become easier to study. The Greek philosopher Aristotle recognised this in the 300s BC. He came up with the first systematic approach to classifying the natural world by placing groups of living things in different hierarchies. However, for the next 900 years, there was no universally accepted system and some species ended up with long, unwieldy names in Latin.

Working in the 1730s, Swedish botanist Carl Linnaeus became frustrated with this. He created a much simpler system, one that used just two parts to name each organism scientifically. The first part is the genus, the collective name for a group of similar species. The second part of the name is the species name for that particular organism. This system is called binomial nomenclature and assigns one of these two-part names to every full species, although a third part is added for subspecies.

Binomial nomenclature humpback whale
Scientists now believe there are three subspecies of humpback whale, each with its own three-part scientific name

These scientific names are always written in italics, with the genus capitalised, but not the species part. There are also strict rules governing how they are created. Some people make the mistake of calling them Latin names. However, although they use Latin grammatical conventions, many of the names contain words from other languages, such as Greek. The Linnaean system is still in use today, although many of the thousands of species he himself named have been renamed. This is inevitable as we learn more about the relationships between organisms, particularly through advances in the study of DNA.

The Problem with Common Names: I

You might still be asking why not just use common names? Common names are usually fine for everyday use, such as to tell some you have just seen a tiger, for example. But when working accurately in a scientific context, such as carrying out a bird survey, they can be confusing due to the fact that nobody regulates them. This in turn leads to a number of issues. One of these is that species that look superficially similar but have no connection to each other can end up with the same common name.

American robin
The American robin is no relation to the Eurasian species

Take the American robin. This North American species has an orangey-red breast just like our Eurasian robin. However, they are not actually closely related, and the American bird was named purely because it resembled the European one. Just going by the common names, people might be confused about their relationship. The American robin’s scientific name, Turdus migratorius, tells us, though, that it is a member of the thrush genus Turdus. The Eurasian robin’s name, Erithacus rubecula, reveals that it not part of the same group. It is actually related to chats and flycatchers.

Rowan or mountain ash
The tree we call mountain ash is confusingly neither an ash nor the only tree with this name

Another example of this sort of confusion is the mountain ash. More than one species in the Sorbus genus of trees, including the one we also call rowan, have this common name. And it is confusing for other reasons. First, mountain ashes are not related to true ash trees at all. Second, in Australia, there is a eucalyptus tree, Eucalyptus regnans, also called mountain ash.

The Problem with Common Names: II

Another problem with common names is that a single organism can end up with lots of different names, again because no one regulates them. Some of these variations are regional and are especially noticeable where something has a very large range. One example of this is the mountain lion, a large cat living in the Americas from as far north as Canada to the bottom of Chile. Because of its huge range, it has accumulated different common names in different places including puma, cougar, catamount and panther. We can avoid confusion by using the scientific name, Puma concolor so that everyone knows exactly what species is being referred to.

Binomial nomenclature dunnock
In the past, more people used the name hedge sparrow for the dunnock

Common names can also change over time. Sometimes this is because understanding of a plant or animal’s relationship with others has become clearer. In the UK, another name for the dunnock, Prunella modularis, is the hedge sparrow. The latter name has fallen out of fashion to a certain extent because we now know the bird isn’t related to sparrows, despite the superficial resemblance. Some people do still use both names interchangeably, though, so the scientific name is useful for avoiding confusion.

Cuckoo flower
Cuckoo flower has numerous common names

Some of our plants have a large number of alternative names. For example, the cuckoo flower, Cardamine pratensis, is also known as lady’s smock, mayflower and milkmaids. Fox-and-cubs, Pilosella aurantiaca, is a non-native flower from Continental Europe, but naturalised across the UK. Some of its many names include orange hawkweed and devil’s paintbrush. Only by using their scientific names can we make it clear what plant we are talking about because each has only one of these.

Scientific Names as Descriptive Tools

As well as helping us avoid confusion, scientific names can often give us some useful information about the species they refer to. Sometimes the names contain clues to appearance, including colour or shape. The foxglove’s scientific name, for instance, is Digitalis purpurea. The genus name comes from the Latin for finger, digitus, and refers to the fact the flowers are finger-like. The species name, meanwhile, is the Latin for purple, telling us what colour the flowers are. Other words to look out for in scientific names include ‘hirsutum’, which tells us that some part of the organism is hairy, and ‘maculatum’ or ‘maculatus’, which means it is blotchy.

Foxgloves
The scientific name for foxgloves tells us a lot about its appearance

Scientific names can also tell us about a species’ preferred habitat. Going back to our cuckoo flower, the pratensis part of the name refers to the fact that the plant is generally found in meadows, the Latin meaning of the word. The scientific name of thrift, one of our prettiest coastal flowers, is Armeria maritima which also tells us where we can expect to find it: in maritime habitats. Likewise, the second part of the house martin’s name, Delichon urbicum, refers to the fact it often nests in towns or ‘urban’ environments. More generally, some names refer to a species’ range. The Atlantic puffin only breeds in northern part of the ocean, reflected in the second part of its scientific name, Fratercula arctica.

House martins
House martins are often urban nesters, which their scientific name reflects

Tautonyms

One last element of binomial nomenclature is the tautonym. This is where both parts of the scientific name, the genus and species names, are identical. These aren’t permitted in botanical naming, although single letter differences between name parts are allowed. There are plenty of tautonyms from the world of birds and animals, though. Red fox (Vulpes vulpes), Eurasian otter (Lutra lutra) and magpie (Pica pica) are a few examples.

Red fox
The scientific name for red fox is a tautonym

In binomial nomenclature, tautonyms indicate that the species concerned is what is known as the type species of a genus. This is the most typical species of a particular genus whose characteristics are what define and name it.