(n.) One of the twelve portions into which the year is divided; the twelfth part of a year, corresponding nearly to the length of a synodic revolution of the moon, -- whence the name. In popular use, a period of four weeks is often called a month.

abundant year academic year annum bissextile year calendar month calendar year century common year day decade decennary decennium defective year fiscal year fortnight hour leap year lunar month lunar year lunation luster lustrum man-hour microsecond millennium millisecond minute moment moon quarter quinquennium regular year second semester session sidereal year solar year sun term trimester twelvemonth week weekday year