| Oak. Roble. |
| Oakum. Estopa para calefatear. |
| Obelisk. Obelisco. |
| Oblique. Oblicuo. |
| Obliquity. Esviaje. |
| Octastyle. Octástilo. |
| Odds. Desigualdad, impares. |
| Odeon. teatro griego. |
| Off. fuera de lugar. |
| Office. reposteria. |
| Offset. Modillon, can, repisa. |
| Ogee arch. Arco conopial. |
| Ogival. Ojival. |
| Ogive. Arco apuntalado. |
| Oil. Aceite, engrasar. |
| Open slanting. Empizarrado, |
| Oen well stair. Escalera de ojo. |
| Order of architecture. Orden |
| Oriel window. Ventana circular. |
| Orientation. Orientacion. |
| Outside shutter. Contraventana. |
| Overdoor. Friso de puerta. |
| Overflow pipe. tubo de |
| Overhanging. Alero corrido. |
| Oversailing. Hilada volada. |
| Ovolo moulding. Cuarto de bosel, |
| Outflow. Salida de liquido, |
| Outgoing. Saliente, cesante. |
| Outhouse. Casa pequeña |
| Outle. Desague, portillo. |
| Outline. Contorno, dibujo. |
| Outlook. Ventana, lo que se ve. |
| Outpart. Parte exterior. |
| Outporch. Portico exteior. |
| Outskirt. Arrabal, suburbio. |
| Outwall. Antemural, pared |
| Overflow. Inundar. |
| Overlong. Celador, inspector. |
| Owner. Dueño, propietario. |
| Oxide. Oxido. |
