| fr |
de |
en |
it |
es |
pt |
| Obturateur (m) | Ladenverschluss (m) | Shutter catch / Shutter closure | Otturatore | Obturador (m) | Obturador (m) |
| Octogone (m) | Oktagon (nt) / Achteck (nt) | Octagon | Ottagono (m) | Octógono (m) | |
| Olive de fenêtre (f) | Fensterolive (f) | Fenster olive | Finestra oliva | Aceituna de ventana (f) | |
| Onglet (m) / Mitre (f) / Assemblage à onglet (m) | Gehrung (f) / Gehrungverbindung (f) | Mitre / Miter / Mitre joint | Taglio obliquo (m) / Mitria / Incastro a taglio obliquo (m) | Inglete (m) / ángulo (m) / Unión a inglete (f) | |
| Opacité (f) | Deckkraft (f) | Covering power / Opacity | Opacità (f) | Poder cubriente (m) | |
| Opisthodomos Tempel | Opisthodomos Tempel | Opisthodomos Tempel | Opisthodomos Tempel | Opisthodomos Tempel | |
| Or (m) | Gold (nt) | Gold | Oro (m) | Oro (m) | |
| Ordre composite (m) | Kompositkapitell (nt) / komposite Ordnung (f) | Composite order | Ordine composito | Orden compuesto (m) | |
| Ordre corinthien (f) | Korinthisches Kapitell (nt) / Korinthische Ordnung (f) | Corinthian Capital / Corinthian Order | Ordine Corinzio (f) | Orden Corintia (f) | |
| Ordre des colonnes (m) | Säulenordnung (f) | Order / Order of columns | Ordine delle colonne | Orden de columnas (m) | |
| Ordre ionique (m) | Ionische Ordnung (f) | Ionic order | Ordine ionico (m) | Orden iónico (m) | |
| Oreiller (m) | Kissen (nt) | Cushion / Pillow | Cuscino (m) | Almohada (f) / Cojín (m) / Almohadilla (f) | |
| Organismes biologiques (m.pl) | Bioorganismen (m.pl) | Biological organisms (pl) | Organismi biologici (m.pl) | Organismos biológicos (m.pl) | |
| Orpiment (m) | Auripigment (n) | Auripigment | Orpimento (m) | Oropimente (m) | |
| Outil (m) / Moyen (m) / Auxiliaires (m.pl) | Hilfsmittel (nt) | Tool / Aid / Means | Ausili / Ausilio (m) | Herramienta (f) / Instrumento (m) / Ayuda (f) / Remedio (m) | |
| Oxygène (m) | Sauerstoff (m) | Oxygen | Ossigeno (m) | Oxígeno (m) | |
| oxydation | brandfördernd (adj) | oxidizing | ossidante | oxidante | |