| Nominative | proterozoikum |
| Genitive | proterozoika |
| Dative | proterozoiku |
| Accusative | proterozoikum |
| Vocative | proterozoikum |
| Locative | proterozoiku |
| Instrumental | proterozoikem |
| Nominative | proterozoika |
| Genitive | proterozoik |
| Dative | proterozoikům |
| Accusative | proterozoika |
| Vocative | proterozoika |
| Locative | proterozoikách |
| Instrumental | proterozoiky |