- pertaining to a month, or to each month.
- done, happening, appearing, etc., once a month: a monthly magazine.
- computed or determined by the month: a monthly salary.
- continuing or lasting for a month.
noun, plural month·lies.
- a periodical published once a month.
- Sometimes monthlies. Informal. a menstrual period.
- once a month; by the month.
- occurring, done, appearing, payable, etc, once every month
- lasting or valid for a montha monthly subscription
- once a month
noun plural -lies
- a book, periodical, magazine, etc, published once a month
- informal a menstrual period
adv.1530s, from month + -ly (2). As an adjective from 1570s. Old English had monaþlic, but the modern words seem to be separate formations.