Two terms for "fire" are reconstructible for Proto-Indo-European: *h₁n̥gʷnis and *péh₂ur. They are usually considered in semantic opposition. The first term is usually masculine and refers to fire as something animate and active (compare Agni, the most prominent Old Indic deity), whereas the second term is neuter and refers to fire as something inanimate and passive, i.e. as a substance.
- *h₁n̥gʷnis (animate noun also meaning "fire")
- Hittite: 𒉺𒀪𒄯 (paḫḫur)
- Old Prussian: panno
- Germanic: *fōr (from *ph₂wṓr < *péh₂wōr) (see there for further descendants)
- Ancient Greek: πῦρ (pûr)
- Slavic: *pyrь