The term PART OF AD can be solved by two crossword solutions: DEE (3 letters) and ANNO (4 letters). DEE is an abbreviation for the Latin phrase 'Dies Est Extremis, ' which translates to 'This is the last day.' It is commonly used in legal documents to indicate a deadline or expiration date. ANNO is an abbreviation for the Latin phrase 'Anno Domini, ' which translates to 'In the year of our Lord.' It is commonly used to denote a specific year in the Christian calendar.