From Gaulish, from Proto-Celtic *-ākos (adjective-forming suffix).
-ācus (feminine -āca, neuter -ācum); first/second-declension suffix
In toponyms, mainly in northern Gaul, -ācus is commonly found appended to personal names, denoting the owner of a property or fundus. Rendered -ac, -at, -y, -é in modern French toponyms.
First/second-declension adjective.
| singular | plural | ||||||
|---|---|---|---|---|---|---|---|
| masculine | feminine | neuter | masculine | feminine | neuter | ||
| nominative | -ācus | -āca | -ācum | -ācī | -ācae | -āca | |
| genitive | -ācī | -ācae | -ācī | -ācōrum | -ācārum | -ācōrum | |
| dative | -ācō | -ācae | -ācō | -ācīs | |||
| accusative | -ācum | -ācam | -ācum | -ācōs | -ācās | -āca | |
| ablative | -ācō | -ācā | -ācō | -ācīs | |||
| vocative | -āce | -āca | -ācum | -ācī | -ācae | -āca | |
From Ancient Greek -ακός (-akós, adjective-forming suffix).
-acus (feminine -aca, neuter -acum); first/second-declension suffix
First/second-declension adjective.
| singular | plural | ||||||
|---|---|---|---|---|---|---|---|
| masculine | feminine | neuter | masculine | feminine | neuter | ||
| nominative | -acus | -aca | -acum | -acī | -acae | -aca | |
| genitive | -acī | -acae | -acī | -acōrum | -acārum | -acōrum | |
| dative | -acō | -acae | -acō | -acīs | |||
| accusative | -acum | -acam | -acum | -acōs | -acās | -aca | |
| ablative | -acō | -acā | -acō | -acīs | |||
| vocative | -ace | -aca | -acum | -acī | -acae | -aca | |