Latin word quia comes from Proto-Indo-European *kʷe-, Proto-Indo-European *kʷo-, Proto-Indo-European *kʷ-, and later Proto-Italic *kʷoi (Who, what (relative, indefinite).)
| Dictionary entry | Language | Definition |
|---|---|---|
| *kʷe- | Proto-Indo-European (ine-pro) | |
| *kʷo- | Proto-Indo-European (ine-pro) | |
| *kʷ- | Proto-Indo-European (ine-pro) | |
| *kʷód, kʷod | Proto-Indo-European (ine-pro) | |
| *kʷís | Proto-Indo-European (ine-pro) | Who, what (interrogative). Who, which, that (relative) Which, what. |
| *kʷoi | Proto-Italic (itc-pro) | Who, what (relative, indefinite). |
| quei | Old Latin (itc-ola) | (relative) who, what, that, which (interrogative) who, what, that, which. |
| *kʷis | Proto-Italic (itc-pro) | Who, what (interrogative). |
| qui | Latin (lat) | (interrogative) who, what, which (relative) who, that, which. |
| quia | Latin (lat) | Because, wherefore, for (as conjunction). That. |