Latin noun endings

The five-declension system

In Latin morphology, distinctions between nouns are based on case endings. There are 5 declensions in total. The main diagnostic feature for determining the declension of a specific word is the genitive singular ending (Gen. sing.):

• 1st declension: genitive ending -ae (example: costa, ae f);
• 2nd declension: ending -i (example: musculus, i m);
• 3rd declension: ending -is (example: canalis, is m);
• 4th declension: ending -us (example: cornu, us n);
• 5th declension: ending -ei (example: facies, ei f).

Structure of the dictionary form

To use a noun correctly, it is necessary to know its full dictionary entry. It consists of three mandatory components:

1. The nominative singular form (Nom. sg.).
2. The genitive singular ending (Gen. sg.) or the final part of the stem if it changes in oblique cases.
3. The designation of grammatical gender (m, f, or n).

Grammatical gender is determined by a number of features. For example, the overwhelming majority of words with the ending -us belong to the masculine gender, yet they may be distributed between the 2nd and 4th declensions. Neuter nouns ending in -us are identified exclusively by their dictionary form and belong to the 3rd declension. Nouns with the endings -um or -on invariably belong to the neuter gender and the 2nd declension.

Formulation of drug names

In domestic practice, the names of new medicinal products are approved via two interchangeable transcription equivalents—in Russian and in Latin. The Latin name of the drug is formulated as a neuter noun of the 2nd declension.

In the nominative singular (Nom. sing.), such names have the ending -um, and in the genitive singular (Gen. sing.), the ending -i. Examples include the names Bercarolum, Rifampicinum, and Isadrinum. In prescriptions and medical texts, this is reflected in fixed combinations, for example: Asparcamum (Asparcam) changes to tabulettae Asparcami (Asparcam tablets).

Class and exam questions

What else to study on this topic

• Determining the grammatical gender of nouns by their endings
• Features of the word stem when inflected by cases
• Characteristics of masculine nouns ending in -us
• Neuter words ending in -en and -u
• Differences between the 2nd and 4th declensions for words ending in -us

Other topics in the "Additional Topics" section

Prepared by WhiteCoat Pro faculty in accordance with the medical school curriculum. For educational purposes only.