ad ad /æd/

noun

1. () [Informal] A public promotion of some product or service  ( advert [British] , advertizement [American, Non-standard] , advertizing [American, Non-standard] , ad [Informal] , advertisement , advertising )
   a public promotion of some product or service
    I saw an advertisement for a new movie during the commercial break
   I saw an advertisement for a new movie during the commercial break
   
   

 AD

adverb

1. In the Christian era; used before dates after the supposed year Christ was born  ( A.D. , AD , anno Domini , year of our Lord )
   in the Christian era; used before dates after the supposed year Christ was born
    In AD 200
   in AD 200