See also: Appendix:Variations of "ad"
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- Latin anno Domini, in the year of the Lord or 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 2019.
- 1 Jan. AD 250.
- From the 2nd century BC to the 3rd century AD.
- The Chicago Manual of Style as well as most house styles requires placing the AD before the number of the year and BC after, although in casual use either abbreviation can be found in either place.
- Some use CE, for "Common Era", which is more secular in nature, to avoid potential Christian bias.
- "AD" is not normally used in expressions like "in the year AD 1990", since in such a year it is taken for granted (and it is also redundant, literally meaning "in the year in the year of our Lord 1990"). In "Vesuvius erupted in AD 79", it is expected.
- (anno Domini): AC, A.C. (anno Christi); anno Domini, Anno Domini, CE, Christian Era, in the year of our Lord
AD (plural ADs)
- Assitant director.
- (military) Air defence or air defense.
- (US, Navy) Auxiliary destroyer - a naval tender, a destroyer tender that tends to destroyers.
- (uncountable) Alzheimer's disease.
- (aviation) Initialism of .
- (destroyer tender): AS