scientific name usage

Scientific Name Usage


Non-biologists, including highly trained scientists in other fields, often get confused by scientific names and their usage.  This posting is intended to help.

Take a familiar plant, the tomato.  The name you usually see is Lycopersicon esculentum Miller.  This means that the genus—the general category of similar, very closely related plants, is Lycopersicon, which means “wolf peach,” probably in honor of the once-believed toxic qualities of the plant.  The species name, esculentum, means “good to eat.”  Miller was the guy who gave it that name.

You may also see it as Lycopersicon lycopersicum (L.) Karsten ex Farwell.  This is a synonym, abbreviated syn.  The L. stands for Linnaeus—everybody knows about him so nobody spells his name out.  But he put the plant in a different genus (Solanum, I think) and Karsten, with Farwell, gave it the new genus name.  Then at some point people found something wrong with this name—I don’t know what—and Miller renamed it.  But some people still use the old name, so the synonymy must be recorded.

Zoologists never cite the authorities (the name authors) unless they are doing formal taxonomic writing, but botanists usually cite them.  Trained more in zoology, I find it maddening to have to worry about the authorities, so I just leave them out.

Some species may have subspecies: very slightly different forms that can still all breed with each other and produce perfectly viable offspring.  One of these, the source subspecies of the first individual to be scientifically described, gets the species name doubled:  Passerella iliaca iliaca, eastern fox sparrow.  Others get different names: Passerella iliaca megarhyncha, large-billed (or Sierra Nevada) fox sparrow.  This can be abbreviated P. i. megarhyncha if you are talking about fox sparrows already, and have given the full name.

Varieties are abbreviated var., as in Beta vulgaris var. cicla L, Swiss chard, and Beta vulgaris var. rapa Dumont, sugar beet.  (Since these are plants, I have to cite the authorities.)  Hybrids are designated by x: Triticum x aestivum L., bread wheat, usually without the x but is a known hybrid of several species.  If you know the species you can have Calypte costae x Calypte anna for the hybrid Costa’s with Anna’s hummingbird that we sometimes see in California.

The actual scientific name is always italicized, but the authorities are not.  The authorities are not part of the actual name, and thus have to be in ordinary type font.  The genus name is always capitalized, even in the middle of a sentence.  The species name is never capitalized in zoology, but in botany the species name is capitalized if it’s derived from the name of a person or of a specific place.  Very general place names like americanum are not capitalized.

Scientific names have to be in Latin, or Latinized versions of words in other languages—Lycopersicon is actually Greek but Latin borrowed Greek words all the time, so no one cares.  Much more exotic names get into usage—many Native American, Australian aboriginal, and other  plant and animal names have been Latinized, as in Puma concolor (“puma” is Quechua) or Felis yaguaroundi for the jaguarundi (a Tupi-Guarani name).  And then there is the recent Confuciusornis for a genus of fossil birds from China….

Originally, scientific descriptions had to be in Latin too, and a plant, animal or fungus was not recognized by international science till a Latin description was published.  Some nostalgic scientists still publish in Latin, but English and other international languages are now accepted.

The modern scientific naming system was developed by Linnaeus in the 18th century, but he consciously followed a long line of forebears, from the great ancient Greek botanist Theophrastus (4th century BCE) down to John Ray and others in the 17th century.  Linnaeus sensibly conserved the old names whenever he could; many go right back to Theophrastus, who was an excellent botanist.  Linnaeus set up the formal binomial system described above, and the hierarchy of Kingdom, Phylum, Class, Order, Family, Genus and Species—note the way it follows the “Old Regime” social system!  (There are also suborders, superfamilies, subgenera, etc., etc.)  Traditional naming systems—including the ancient Greek one Theophrastus used—tend to fall into a very similar pattern: a folk genus with folk species and sometimes folk subspecies and varieties, subsumed under broader categories like “bird” and “snake.”

Humans are Kingdom Animalia, Phylum Cordata (animals with spinal cords), Class Mammalia, Order Primates, Family Hominidae, Genus Homo, species sapiens.  Modern humans should probably be subspecies H. s. sapiens, with Neanderthals and other extinct forms as other subspecies, but many writers keep these various forms as separate species.  There is a huge controversy about just what a “species” is when you’re talking about fossil forms.  Some, “splitters,” would give new names to every vaguely-different-looking skull.  Others, “lumpers,” infer relationships from basic similarities, and use names much more widely.  Even in living species there is constant disagreement about exact species boundaries, usually when two populations hybridize a bit but not regularly.  Splitters then separate them, lumpers lump them into one species.  Splitting and lumping tend to run in cycles; the Baltimore oriole has been lumped with the Bullock’s oriole about half my life, and split the other half (when I was young and again when I got old).  This is a pretty common story.

Modern genetics, especially population genetics and genomics, has tremendously improved our understanding of species, genus, and higher-level boundaries!  This (with some old-fashioned anatomical study) explains the many changes in scientific names that you will have seen if you work with such materials. Plant lovers in particular have had to deal with this.  For one example, the old lily family has been broken up into many small families—the plants in the new families look sort of alike but are quite different genetically.  Onions and garlic, for instance, were formerly lilies, but now have a family of their own, distinguished by the chemicals that give them their scent.  Much remains to be done as more genomic information comes out.

Sometimes, habit is so strong that an invalid scientific name persists.  The dog is usually still Canis familiaris (as named by Linnaeus), but it is really just a domesticated wolf, and thus is really Canis lupus.  Maybe it should be “var. familiaris.


The plural of “genus” is “genera.”  The singular and plural of “species” are both “species.”  (“Specie” is an unrelated word; it means money.)  Both of these plurals are quite unusual forms for Latin, which causes yet more confusion.  It may be useful to know that the usual Latin masculine ending is –us, feminine –a, neuter –um; corresponding Greek endings are –os, -a, -on; plural of the neuter in both languages is –a (as in genera), which can be confusing.  Tree species names are usually in the feminine, because the Latins believed trees had female spirits living in them.  So, e.g., Pinus ponderosa, though Pinus has the masculine ending.


Scientific names follow a rule of priority: the name given when the species was first described must be used forever.  There are very few exceptions.  These occur mostly when the description was too poor to be regarded as adequate, and no type specimen was saved.  Even the sacred Linnaeus was prone to this—his name Achras sapota for the chicozapote was considered so bad that it was renamed (with a new, split genus) Manilkara achras (Mill) Fosberg.  However, most botanists are enough in awe of Linnaeus to keep calling it Manilkara sapota (L.) Van Royen.   Note, again, Linnaeus’ and others’ fondness for local names; sapota is from Nahuatl tzapotl, meaning any soft fruit.

If the original description was so bad that nobody can figure out what it applied to, the name can become a nomen nudum—a “naked name,” without a real application.  Usually, though, there is another name available for the species in question.  Sometimes a very obscure earlier name and description are discovered in some old tome.  This should mean that the long-established name should be killed, but the international nomenclature commissions can be charitable, and spare a long-established name.


For every scientific name, there has to be a “type specimen”: An actual example of the species (or genus or subspecies), preserved in a museum, herbarium, or similar archive.  This should, and almost always is, be the individual on which the original Latin description was based.  This applies to fossils as well as to living species.  This allows checking back.  If geneticists determine that a species has to be split into two or three, for instance, you want to know which of those two or three the original type was, so you go back and look at it.  I’m not sure what the type specimen for Homo sapiens is!  If there is no surviving type specimen (as there usually is not for those 18th-century names), a type specimen will have been picked out “by subsequent designation,” as we say in the trade.

Ideally, type specimens, and all other specimens for that matter, are filed away in their storage cases with labels that provide the exact location of collection, with information such as what kind of vegetation was around, what date the item was collected, and other useful data.  We ethnobiologists pray for some indication of how the plant or animal was used!  Some labels do have that!  Always remember to put as much data on a label as you can fit on it, and keep a backup record with even more data (labels do get lost).  If you are doing field work in zoology you probably aren’t collecting much, but if you’re studying ethnobotany, or ethnoentomology or ethnomycology, you have to collect specimens and get them properly identified and archived at local institutions.


Old-fashioned drug names were in Latin too, and can look confusingly like scientific names, e.g. oleum olivarum, olive oil.  The Chinese have most unfortunately revived this custom and given Chinese drugs modern Latin names, e.g. fructus Lycii for goji berries (the fruit of Lycium chinense or L. barbarum).  People, especially Chinese writers, now confuse these with scientific names, creating total chaos, e.g. by mixing up the usage of  fructus Lycii and Lycium chinense as if they were somehow the same thing.  I wish these Chinese drugs had kept their Chinese names.