annum meaning, which is translated to year, is of Latin origin. It is commonly applied in legal, formal or financial language, particularly in such expressions as per annum, or per year. The term assists in stating time related calculations like salaries, interest rates or lease agreements. You find that when you encounter annum in documents, it means a 12-month period that is applicable in budgeting, planning or in performance of the financial performance. Having an idea about annum simplifies deciphering of contracts, comparing costs and handling long term obligations that are based on annual periods.