pentoxide

Etymology tree
Proto-Indo-European *pénkʷe
Proto-Hellenic *pénkʷe
Ancient Greek πέντε (pénte)
Ancient Greek πεντᾰ- (pentă-)lbor.
English penta-
Proto-Indo-European *h₂eḱ-der.?
Ancient Greek ὀξύς (oxús)
Proto-Indo-European *ǵenh₁-
Proto-Indo-European *-os
Proto-Indo-European *ǵénh₁os
Proto-Hellenic *génos
Ancient Greek γένος (génos)
French oxygène
Proto-Indo-European *h₂eḱ-
Proto-Indo-European *-éh₁ti
Proto-Indo-European *-yeti
Proto-Indo-European *-éh₁yeti
Proto-Indo-European *h₂eḱéh₁yeti
Proto-Italic *akēō
Latin aceō
Proto-Indo-European *dʰeh₁-der.
Proto-Italic *-iðos
Latin -idus
Latin acidusbor.
French acide
blend
French oxidebor.
English oxide
English pentoxide
From penta- + oxide.