General information on declensions
There are five declension types in Latin. A noun's declension is determined by its ending in the genitive singular (Genetivus Singularis). Each declension has its own characteristic ending for this case.
- 1st declension — ending -ae
- 2nd declension — ending -i
- 3rd declension — ending -is
- 4th declension — ending -us
- 5th declension — ending -ei
The dictionary form of a noun necessarily includes the nominative form, the genitive ending, and the gender indication, which allows for the precise determination of the declension.
First declension
The first declension includes feminine nouns with the ending -a in the nominative singular and -ae in the genitive. Examples: planta, plantae — plant; vena, venae — vein; terra, terrae — earth; cellula, cellulae — cell.
This declension also includes masculine nouns denoting male persons: agricola — farmer, nauta — sailor, pirata — pirate, poeta — poet, scriba — scribe.
Second declension
The second declension includes masculine and neuter nouns. In the nominative singular, masculine nouns have the endings -us, -er, and neuter nouns have -um, -on.
- Masculine: amicus — friend, puer — boy
- Neuter: colon — colon, folium — leaf
Exceptions to the general rule: vulgus (people, mob) — neuter, and humus (earth, ground) — feminine.
Third declension and its types
The third declension includes nouns of all three genders with various endings in the nominative singular. The unifying feature is the ending -is in the genitive. Three types are distinguished based on the historical stem.
Consonant type
Includes imparisyllabic nouns that have a single consonant sound before the ending -is in Genetivus Singularis. The case endings for masculine and feminine nouns are identical. For neuter nouns, the Accusativus and Vocativus Singularis match the Nominativus, and in the plural these cases end in -a. Dativus and Ablativus Pluralis end in -ibus for all genders. Examples: victor, victoris — victor (m.); miles, militis — soldier (m.); vox, vocis — voice (f.); nomen, nominis — name (n.).
Vowel type
Combines neuter nouns with the endings -e, -al, -ar: mare, maris — sea; animal, animalis — animal; exemplar, exemplaris — specimen, sample. This also includes parisyllabic feminine nouns: turris — tower, puppis — stern, sitis — thirst, febris — fever, securis — axe, as well as names of rivers and cities (Tiberis, Neapolis).
Mixed type
Combines imparisyllabic nouns whose stem ends in two consonant sounds: pars, partis — part; urbs, urbis — city; nox, noctis — night. It also includes parisyllabic nouns ending in -is, -es: avis — bird, nubes — cloud.
Fourth and fifth declensions
K to the fourth declension include masculine and neuter nouns with the ending -us in Genetivus Singularis. In the nominative case, the masculine gender has the ending -us, the middle is -u. Medical vocabulary: fructus — fetus, processus — process, textus — tissue, meatus — passage, meatus, sinus — sinus, arcus — arch, ductus — duct, spiritus — alcohol, usus — use, consumption, gustus — taste.
The fifth declension includes feminine nouns with the ending -es in the nominative and -ei in the genitive: res, rei — thing, circumstance; fides, fidei — trust, faith. The exception is the masculine noun dies (day, term).
Key points
- The declension type is determined by the ending of Genetivus Singularis.
- 1st declension — predominantly feminine, ending -ae.
- 2nd declension — masculine and neuter, ending -i.
- 3rd declension — all three genders, ending -is; divided into consonant, vowel, and mixed types.
- In the 3rd declension of neuter nouns, Nom., Acc., and Voc. coincide, ending in -a in the plural.
- 4th declension — masculine and neuter, ending -us; includes important anatomical terms.
- 5th declension — feminine, ending -ei; exception dies — masculine.
- The dictionary form of a noun includes the Nominativus, the Genetivus ending, and the gender.