This document establishes a vocabulary of terms and semantics for all fields of respiratory care involving mechanical ventilation, such as intensive-care ventilation, anaesthesia ventilation, emergency and transport ventilation and home-care ventilation, including sleep-apnoea breathing-therapy equipment. It is applicable — in lung ventilator and breathing-therapy device standards, — in health informatics standards, — for labelling on medical electrical equipment and medical electrical systems, — in medical electrical equipment and medical electrical system instructions for use and accompanying documents, — for medical electrical equipment and medical electrical systems interoperability, and — in electronic health records. This document is also applicable to those accessories intended by their manufacturer to be connected to a ventilator breathing system or to a ventilator, where the characteristics of those accessories can affect the basic safety or essential performance of the ventilator and ventilator breathing system. NOTE This document can also be used for other applications relating to lung ventilation, including non-electrical devices and equipment, research, description of critical events, forensic analysis and adverse event (vigilance) reporting systems. This document does not specify terms specific to breathing-therapy equipment, or to physiologic closed-loop ventilation, high-frequency ventilation or negative-pressure ventilation; nor to respiratory support using liquid ventilation or extra-corporeal gas exchange, or oxygen, except where it has been considered necessary to establish boundaries between bordering concepts.