Botanical Latin
Lesson 3 - Second Declension Nouns

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(updated 13 July 2022)

The second declension, like the other declensions, has a diagnostic ending in the genitive singular. That ending was -ae in the first declension, and it is (a long i) here in the second one. The second declension is a little more varied than the first.

Almost all first declension nouns are feminine, but all three genders are represented in the second declension. First declension nouns end in -a, but second declension nouns have a nominative singular ending of -us (mostly masculine, some feminine; Tables 3.1 and 3.2), -er (mostly masculine; Tables 3.3 and 3.4), -ir (only one, masculine; described, no table), or -um (neuter; Table 3.5).

-us nouns. To form the second declension of -us nouns, drop the from the end of the genitive singular—this gives you the stem—and add the endings shown in Table 3.1.

Table 3.1 - second declension -us nouns.
case singular plural
nominative stem + us stem + ī
genitive stem + ī stem + ōrum
dative stem + ō stem + īs
accusative stem + um stem + ōs
ablative stem + ō stem + īs

Table 3.2. example: sorus (sorus).
case singular plural
nominative sorus sori
genitive sori sororum
dative soro soris
accusative sorum soros
ablative soro soris

Most second declension nouns that end in -us in the nominative singular are masculine. Notable exceptions are many trees and shrubs (e.g., Alnus, Cedrus, and Cornus), which are feminine. Other exceptions are the feminine nouns humus (ground), hydathodus (hydathode), and methodus (method), and the neuter nouns pelagus (sea) and virus (poison).

-er nouns. The second declension endings of the very few -er nouns in botanical Latin are the same as those for -us nouns (see Table 3.1) except, of course, the nominative singular. There is a difference, however, among -er nouns of the second declension as to whether the e of the nominative singular ending stays in the remaining cases (as well as in the nominative plural) or whether it is dropped. Congener, for example, keeps the e, making the rest of the declension congeneri, congenero, etc. On the other hand diameter drops the e and the declension continues diametri, diametro, etc. The only sure way to determine whether an -er noun keeps the e or drops it is to memorize both the nominative singular and genitive singular when you learn the vocabulary. But you should do this anyway in order to determine what declension a noun belongs to. Knowing English words that are derived from Latin is also helpful. From congener comes “congeneric” (with the e), and from diameter comes “diametric” (without the e).

Table 3.3. congener (congener), an -er noun that keeps the e.
case singular plural
nominative congener congeneri
genitive congeneri congenerorum
dative congenero congeneris
accusative congenerum congeneros
ablative congenero congeneris

Table 3.4. diameter (diameter), an -er noun that loses the e.
case singular plural
nominative diameter diametri
genitive diametri diametrorum
dative diametro diametris
accusative diametrum diametros
ablative diametro diametris

-ir noun. The only -ir noun is the masculine vir (man), but this is not found in Linnaeus’s Species Plantarum. It has the same endings as the other nouns described above, except in the nominative singular, which is simply vir.

-um nouns. All second declension -um nouns, including names of genera that end in -um (e.g., Galium), are neuter and have the endings given in Table 3.5. Except for the nominative singular and the nominative and accusative plural, the endings are the same as of the mostly masculine second declension -us and -er nouns. Note that the singular nominative and accusative endings are the same as each other (-um), just as they are (-a) in the plural.

Table 3.5. Second declension -um (neuter) nouns; e.g., folium (leaf).
case singular plural
nominative folium folia
genitive folii foliorum
dative folio foliis
accusative folium folia
ablative folio foliis

Vocabulary entries for nouns in dictionaries, glossaries, and the like give the nominative singular and either the full genitive singular (e.g., congener, congeneri) or an abbreviated form of the genitive singular (e.g., achenium, -i). The full entry of the genitive singular is given if the abbreviated form would create uncertainty. You may wonder how to determine the stem of the noun if only -i is given for the genitive, and if, to determine the stem, you need the full genitive. The rule about dropping the genitive ending becomes particularly important in the third declension, but in the second declension (except for the -er nouns) and the first declension, the stem can be determined simply by dropping from the nominative singular the -us or -um in the second declension and -a in the first.
The gender of each noun is given in parentheses, “m” for masculine, “f” for feminine, and “n” for neuter.
As with other vocabularies in these lessons, only a few words are given. For more words of the second declension, visit the online Botanical Latin Glossary and search for "2nd declension" (without the quotation marks).

achenium, -i (n) – achene diameter, diametri (f) – diameter nodus, -i (m) – node pilus, -i (m) – hair
aculeus, -i (m) – prickle filamentum, -i (n) – filament ovulum, -i (n) – ovule pistillum, -i (n) – pistil
androecium, -i (n) – androecium folium, -i (n) – leaf pappus, -i (m) – pappus racemus, -i (m) – raceme
bulbus, -i (m) – bulb folliculus, -i (m) – follicle pedicellus, -i (m) – pedicel ramulus, -i (m) – branchlet
carpellum, -i (n) – carpel gynoecium, -i (n) – gynoecium pedunculus, -1 (m) – peduncle ramus, -i (m) – branch
congener, congeneri (m) – congener limbus, -i (m) – limb (of a petal) perianthium, -i (n) – perianth scapus, -i (m) – scape
corymbus, -i (m) – corymb lobus, -i (m) – lobe petalum, -i (n) – petal sepalum, -i (n) – sepal
culmus, -i (m) – culm nervus, -i (m) – nerve petiolus, -i (m) – petiole tepalum, -i (n) – tepal

Latin Descriptions and Diagnoses
In lesson 2 you saw the phrase “Latin descriptions and diagnoses” used several times. It seems appropriate, then, to take some time here to explain what a description is and what a diagnosis is. A description is simply a listing of the features of a plant. It can be as simple as planta herba (plant an herb) or it can go on for pages. But whatever their length, they all follow the same pattern: a noun followed by words or phrases that describe that noun, those words or phrases separated by commas, then a semicolon, then another noun followed by descriptors that are separated by commas, and so on. A description might go something like this: plant an annual herb, armed with prickles, synoecious; leaves opposite, pubescent on the abaxial surface, glabrous adaxially; flowers red, with 5 petals, 4 sepals, and 37 stamens; fruit a pink berry, 3–24 mm in diameter, densely covered with bristles. In a description, you essentially start with nothing and slowly build an image of the plant.
   A diagnosis, on the other hand, always begins with a known taxon and proceeds to note how a new taxon of the same rank differs from the known one. An example of a diagnosis for a new species could be: similar to Lentibularum officinale but it [the new species] differs with blue flowers and three fused carpels.

Translate the following into English.
   1. inflorescentia corymbus
   2. petiolus folii
   3. culmus pilis [pilis an ablative]
   4. lamina folii pilis [pilis an ablative]
   5. ramulae plantae
   6. antherae androecii
   7. infructescentia folliculorum
   8. herbae sepalis et petalis et androeciis et gynoeciis [lots of ablatives here]
   9. {?}
   10. aculei pedunculorum

Write the following in Latin.
   1. leaves with spots
   2. a branch's diameter
   3. a petal with a limb
   4. the limb of a petal
   5. a perianth with tepals
   6. the peduncle and pedicels of an inflorescence
   7. inflorescence a raceme
   8. a pappus of bristles
   9. {?}
   10. the nerves of an achene with hairs [note: the intent here is that the hairs are on the nerves]

Write a Latin description for the following. These are more challenging. You have to convey the meaning rather than following the exact wording.
   1. an herbaceous plant that has lobed leaves
   2. {?}