Latin Noun Declension
Decline any regular Latin noun across all six cases.
Stem: rēg- (derived from the genitive)
| Case | Singular | Plural |
|---|---|---|
| Nominative | rēx | rēgēs |
| Genitive | rēgis | rēgum |
| Dative | rēgī | rēgibus |
| Accusative | rēgem | rēgēs |
| Ablative | rēge | rēgibus |
| Vocative | rēx | rēgēs |
Covers regular consonant-stem nouns. I-stem 3rd-declension nouns (e.g. -ium genitive plural) and other exceptions may differ.
To decline a Latin noun, use the genitive singular ending to identify its declension, strip that ending to get the stem, then add the case endings. For puella, puellae (1st declension), the stem puell- gives accusative singular puellam and genitive plural puellārum.
How declension works
Latin marks a noun’s role in the sentence with its ending, not its position — so word order is free. There are five declensions, and the genitive singular ending tells you which one a noun belongs to: -ae (1st), -ī (2nd), -is (3rd), -ūs (4th), -ēī (5th). Strip the genitive ending to get the true stem, then add the case endings. The tool keeps your nominative verbatim, so irregular nominatives (rex, corpus, puer) stay correct.
Genitive ending → declension
The genitive singular reveals the declension and gives the stem.
| Declension | Genitive sg | Example |
|---|---|---|
| 1st | -ae | puella, puellae (f) |
| 2nd | -ī | dominus, dominī (m) |
| 3rd | -is | rex, regis (m) |
| 4th | -ūs | manus, manūs (f) |
| 5th | -ēī / -eī | rēs, reī (f) |
1st-declension case endings
Nominative and vocative singular use the noun’s given nominative form verbatim.
| Case | Singular | Plural |
|---|---|---|
| Nominative | -a | -ae |
| Genitive | -ae | -ārum |
| Dative | -ae | -īs |
| Accusative | -am | -ās |
| Ablative | -ā | -īs |
| Vocative | -a | -ae |
Worked example: puella, puellae, f (girl)
The genitive puellae ends in -ae, so this is 1st declension. Drop -ae to get the stem puell-, then add the endings above.
| Case | Singular | Plural |
|---|---|---|
| Nominative | puella | puellae |
| Genitive | puellae | puellārum |
| Dative | puellae | puellīs |
| Accusative | puellam | puellās |
| Ablative | puellā | puellīs |
| Vocative | puella | puellae |
- 1 Identify the declension from the genitive singular. The genitive-singular ending marks the class — -ae is 1st, -ī is 2nd, -is is 3rd, -ūs is 4th, and -ēī is 5th (puella, puellae → 1st).
- 2 Find the stem. Remove the genitive-singular ending from the genitive form — puellae drops -ae to give the stem puell-.
- 3 Note the noun’s gender. Gender changes some endings — neuter nouns in the 2nd, 3rd, and 4th declensions share nominative and accusative and take a plural in -a.
- 4 Add the case ending you need. Attach the ending for the target case and number to the stem — puell- + -am gives the accusative singular puellam, and + -ārum the genitive plural puellārum.
- 5 Choose the case by the noun’s role. Let the noun’s job in the sentence pick the case — subject → nominative, direct object → accusative, possession → genitive, and so on.
Where the rules break down
Gender changes the neuter forms. Neuter nouns in the 2nd, 3rd, and 4th declensions have a nominative = accusative, and a plural in -a (or -ua). That is why the tool asks for gender.
I-stem nouns. The tool declines regular consonant-stem 3rd-declension nouns. I-stem nouns (genitive plural in -ium, neuter ablative singular in -ī) and other exceptions can differ and are noted rather than auto-applied.
Irregular nominatives. Because the nominative you type is used as-is, forms like rex (stem reg-) and corpus (stem corpor-) stay correct even though the stem looks nothing like the nominative.
Once the noun cases make sense, pair them with the Latin conjugator for verbs, or brush up on the Greek alphabet for the classics.