Genu, genus
Genus is a fourth declension noun. Fourth declension nouns ending in -u in the nominative singular decline like this. They all neuter in gender.
| Case | Singular | Plural |
|---|---|---|
| Nom. | genu | genua |
| Voc. | genu | genua |
| Acc. | genu | genua |
| Gen. | genus | genuum |
| Dat. | genu | genibus |
| Abl. | genu | genibus |