The full form of AD is Anno Domini, which is a Medieval Latin term meaning "in the year of the Lord". It is used to label or number years in the Julian and Gregorian calendars, and counts years from the traditionally reckoned year of the birth of Jesus. The terms BC (Before Christ) and AD (Anno Domini) are used to denote the years in the Julian and Gregorian calendars. The abbreviation "AD" is also widely used after the number of a century or millennium.