| Subject | English | Bulgarian |
| construct. | open construction system | отворена строителна система |
| construct. | open heat-supply system | отворена топлоснабдителна система |
| construct. | open steam-heating system | разчленена парна отоплителна система |
| construct. | open system of typification | отворена система на типизация |
| comp., MS | Open Systems Interconnection model | Отворен модел за връзка между мрежови системи (A networking model introduced by the International Organization for Standardization (ISO) to promote multi-vendor interoperability. OSI is a seven-layered conceptual model consisting of the application, presentation, session, transport, network, data-link, and physical layers) |
| commun., comp. | open systems interconnection reference model | еталонен модел за открити мрежи |
| commun., comp. | open systems interconnection reference model | еталонен седемслоен модел OSI |
| gen. | open systems interconnection reference model | еталонен модел OSI-ISO |
| vent. | open-type exhausting system | отворен смукач |