Romanian word cu comes from Proto-Indo-European *kʷe-, Proto-Indo-European *kʷo-, Proto-Indo-European *ḱe, Proto-Indo-European *ḱón, and later Proto-Indo-European *ḱóm (Beside, near, by, with.)
| Dictionary entry | Language | Definition |
|---|---|---|
| *kʷe- | Proto-Indo-European (ine-pro) | |
| *kʷo- | Proto-Indo-European (ine-pro) | |
| *ḱe | Proto-Indo-European (ine-pro) | |
| *ḱón | Proto-Indo-European (ine-pro) | |
| *ḱóm | Proto-Indo-European (ine-pro) | Beside, near, by, with. |
| *kʷís | Proto-Indo-European (ine-pro) | Who, what (interrogative). Who, which, that (relative) Which, what. |
| *kom | Proto-Italic (itc-pro) | (with ablative) with, along, at. |
| *kʷis | Proto-Italic (itc-pro) | Who, what (interrogative). |
| cum | Latin (lat) | Although. Because. When With. |
| cu | Romanian (ron) | With. With (in the instrumental sense). |