Scientific Latin: How to Read a Species Name

A scientific name is two Latin words in a grammatical relationship. The genus is a noun with a fixed gender; the epithet after it is usually an adjective agreeing with that noun, sometimes a second noun or a genitive. Learn the three patterns and a field guide stops being vocabulary and starts being information.

Why Latin: 1753 and 1758

Before Linnaeus, a plant's name was a description, a Latin phrase of many words that no two authors agreed on:

• Physalis annua ramosissima, ramis angulosis glabris, foliis dentato-serratis - the old phrase-name.
• Physalis angulata - Linnaeus's two words for the same plant.

Carl Linnaeus did not invent Latin names. He made the two-word name the rule and applied it to every plant and animal he described, in two books that are still the legal starting lines:

The botanical and zoological codes count from those books (for most groups), and of two names for one species the older wins. Marsh named Apatosaurus in 1877 and Brontosaurus in 1879; for a century the 1877 name took the bones, until a 2015 study split them again.

Other species got a description of their features. For Homo sapiens Linnaeus wrote nosce te ipsum: know yourself.

How a species name is written

Two words, two jobs, and four rules of typography:

The epithet stays lower case even when it honours a person: Rafflesia arnoldii is named for Joseph Arnold. And the epithet alone names nothing: there are many species called vulgaris, and only one Thymus vulgaris.

Zoologists call the system binominal nomenclature; botanists say binomial. The two codes have been failing to agree on small things for a century.

The epithet as an adjective

Most epithets are adjectives, and an adjective agrees with its noun in gender. The genus decides the ending: one adjective, three genders.

Two patterns are at work:

• officinalis, officinale - third declension: -is for masculine and feminine, -e for neuter.
• sativus, sativa, sativum - like bonus, bona, bonum.

Homo sapiens agrees too, and shows nothing for it. Sapiens, wise, is a present participle of sapere, third declension, with one nominative singular for all three genders. Beginners who assume epithets never change have been looking at the ones that cannot.

Trees are feminine

Classical Latin tree names in -us are feminine, whatever their declension, so their adjectives end in -a:

The Romans made the tree feminine and its fruit neuter: malus, the apple tree, and malum, the apple; pirus, the pear tree, and pirum, the pear.

Not every tree: Acer, the maple, is neuter, so red maple is Acer rubrum.

Because the code fixes the genus's gender, an adjective epithet is rewritten when a species moves genus. The organism has not changed; the adjective has:

Nouns as epithets: apposition and the genitive

When the epithet is a noun, nothing agrees. It either stands beside the genus in the nominative, naming it again, or sits in the genitive, meaning "of".

Rex is a noun, so it never becomes regis or regem to suit the lizard. Henry Fairfield Osborn named it in 1905.

Vulpes vulpes is a tautonym: allowed in zoology, banned in botany. The queen of Strelitzia reginae is Charlotte of Mecklenburg-Strelitz, which explains the genus too.

Epithets worth knowing

Learn these and you can decode much of any field guide. First, where it lives:

Then what it is like:

Officinalis comes from officina, a workshop, and in medieval Latin the storeroom where medicines were kept: the epithet marks the species the apothecaries stocked. Ursus arctos horribilis, the grizzly, is a trinomial: genus, species, subspecies. George Ord coined horribilis in 1815 for a species of his own; it now ranks as a subspecies of the brown bear.

Anatomy: the genitive at the gym

Many muscle names are a word describing the muscle plus the genitive of the body part it belongs to: the two-headed one of the arm.

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1. 1caput
2. 2os
3. 3manus
4. 4brachium
5. 5pes

Caput, the head; os, the mouth (per os, by mouth); manus, the hand; brachium, the arm (biceps brachii, the two-headed muscle of the arm); pes, the foot.

Digitorum and lumborum are genitive plurals: more than one finger, more than one loin. Biceps is bi- plus caput, two-headed; its plural is bicipites.

Where there is no genitive, there is agreement, feminine on feminine and neuter on neuter:

• vena cava - the hollow vein.
• medulla oblongata - the elongated marrow.
• foramen magnum - the great hole, at the base of the skull.

Prescription Latin

Medical shorthand is one of the few places Latin is still written daily, mostly by people who do not know they are writing it:

Per os is per with the accusative of os, mouth, which looks the same as the nominative. In die is in with the ablative: in a day.

Pro re nata is literally for the matter having arisen. Recipe is an imperative, an order to the pharmacist.

Mistakes English speakers make

What to do next

1. Revise adjective agreement and the genitive: that is all a species name uses.
2. Read Latin phrases used in English for the same grammar in everyday words.
3. Take a field guide outside and parse the small italic type.