| 1 | English | pentoxide | any oxide containing five oxygen atoms in each... |
| 2 | English | oxide | A binary chemical compound of oxygen with another... |
| 3 | French | oxide | Obsolete spelling of oxyde |
| 4 | French | acide | acid, acidic, sour, tart; acid, acidic; acid |
| 5 | Latin | acidus | sour, tart, acid, bitter; harsh, grating, rough,... |
| 6 | Latin | aceō | — |
| 7 | Proto-Italic | akēō | be sharp-tasting, be sour |
| 8 | Proto-Indo-European | h₂eḱ-éh₁-ye-ti | — |
| 9 | Proto-Indo-European | h₂eḱ- | sharp |