Proto-Indo-European Roots
| Root/Stem: | *kwis |
| Meanings: | who, what |
| Cognates: | |
| Hellenic | Greek tis 'who, what' |
| Italic | Latin quis 'who', quid 'what', Oscan pis 'who', pid 'what' |
| Celtic | Old Irish cid 'what' |
| Indic | Sanskrit kis, kim 'who, what' |
| Dardic & Nuristani | |
| Iranian | |
| Anatolian | Hittite & Luwian & Palaic kuis 'who, what', Lydian qi- 'something, whatever', Lycian ti 'which' |
| Tocharian | |
| Armenian | |
| Balkan | |
| Germanic | |
| Baltic | |
| Slavic | Common Slavic *ki-to 'what' > Russian chto 'what' |
| Notes: | This is one of the derivatives of the Indo-European root *kw-, which formed a great lot of pronouns in the languages of the family. English when, where, who, what, which and other pronouns of this kind are all descendants of this *kw-, the same as pronouns of other Indo-European languages. The root was mainly used for forming interrogative and relative pronouns. |