[AIVC, Air infiltration and ventilation glossary, 1992]:heat transmission by mechanically induced movement of a fluid.

[EN 12792:2003, 188]:sum of the cross-sectional areas of all unobstructed openings measured in the plane of maximum restriction and at right angles to the flow through the opening.

[EN 12792:2003, 190]:ratio of the free area to the core area of an air terminal device.