MM is a financial abbreviation. It used to be "the standard" but nowadays they also use M. Compare with the "M" in CPM, which is not the roman 'M' but the Fren

MM is a financial abbreviation. It used to be "the standard" but nowadays they also use M. Compare with the "M" in CPM, which is not the roman 'M' but the French 'Mille'. So, "M" is sometimes ambiguous. In this case it wouldn't be, but I always use mm or MM to mean million, and bn or BN to mean billion.