The fourth declension consists of mostly masculine nouns.
The masculine and feminine nouns decline in the same way, but the neuter nouns decline differently.
You can find the stem of a fourth declension noun by removing the -ūs in its singular genitive form.
Notable exceptions are domus, domūs, f. (house); manus, manūs, f. (hand).
senatus, senatūs, m. (Senate)
| Singular | Plural | |||
|---|---|---|---|---|
| Nominative | senatus | senatūs | ||
| Genitive | senatūs | senatuum | ||
| Dative | senatuī | senatibus | ||
| Accusative | senatum | senatūs | ||
| Ablative | senatū | senatibus | ||
| Vocative | senatus | senatūs |
genū, genūs, n. (knee)
| Singular | Plural | |||
|---|---|---|---|---|
| Nominative | genū | genua | ||
| Genitive | genūs | genuum | ||
| Dative | genū | genibus | ||
| Accusative | genū | genua | ||
| Ablative | genū | genibus | ||
| Vocative | genū | genua |