- (initialism) . Latin ''anno Domini'', in the year of our Lord, used to specify numbered years counting from the once estimated birth of Christ in year 1. Usually placed before years (but see notes), and always placed after centuries. Often written in small caps. This year is AD (CURRENTYEAR) .
- (initialism) . assistant director.
- (initialism) . (military) air defence or air defense.
- (initialism) . antidepressant.
- (initialism) . (US, Navy) Auxiliary Destroyer - a naval tender, a destroyer tender that tends to destroyers.
- Noun. (informal) Short form of advertisement.
- Noun. (tennis) advantage.
- Preposition. to, toward .