- or AD1) use in the year of the Lord; since Christ was born: Charlemagne was born in a.d. 742Etymology: L annō Dominī2) gov assembly district3) spo athletic director•usage: The abbreviation a.d. was orig. placed before a date and is still usu. preferred in edited writing: The Roman conquest of Britain began in a.d. 43 (or, sometimes, began a.d. 43). The abbreviation b.c. (before Christ) is always placed after a date: Caesar was assassinated in 44 b.c. But by analogy with the position of b.c., a.d. is frequently found after the date in all types of writing: Claudius I lived from 10 b.c. to 54 a.d. This abbreviation may also designate centuries, being placed after the century specified: the second century a.d. Some writers prefer to use c.e. (Common Era) and b.c.e. (Before the Common Era) to avoid the religious overtones of a.d. and b.c.
From formal English to slang. 2014.