| Subject | English | German |
| med. | angular aperture | a |
| nat.sc. | angular aperture | Öffnungswinkel |
| hi.energ. | angular aperture | Winkelapertur |
| hi.energ. | angular aperture | Winkelöffnung |
| microel. | angular aperture | Winkelblende |
| opt. | angular aperture | Öffnungswinkel (microscope: the angle of the largest cone of light entering the objective from an object point on the axis) |
| tech. | angular aperture | Objektivoeffnungswinkel |
| med. | angular aperture | Aperturwinkel |
| opt. | exit pupil angular aperture | Öffnungswinkel der Austrittspupille |
| opt. | half of the angular aperture | halber Öffnungswinkel |
| opt. | sine of half the angular aperture | Sinus des halben Öffnungswinkels |