Definition of lunar month in US English:

lunar month


  • 1A month measured between successive new moons (roughly 291/2 days).

    • ‘The Babylonians had found a cycle of 223 lunar months within which eclipses of sun and moon recur at equal intervals and Thales had discovered this formula.’
    • ‘Each lunar month starts on the day of the new moon.’
    • ‘For instance, if the ratio of gears of a clock produces 29.5 days per lunar month; that's okay for a short period of time, but over 10,000 years the number 29.5305882 is a much better choice.’
    • ‘An intercalary month was added every three years to allow for the fact that a solar year has 365.2422 days while 12 lunar months of 29.5306 days contains 354.3672 days.’
    • ‘Like the rise and the fall of the currents, the length of each day, each lunar month and each year is related to the waxing and the waning of the moon and the sun, and the rotation of the earth.’
    • ‘It is the vital data from which the calendrical relationships between sun and moon cycles may be understood - and therefore the most important piece of numerical data after the number of days in a lunar month and the length of the solar year.’
    • ‘During this period - one Metonic cycle - there are precisely 235 lunar months.’
    1. 1.1 (in general use) a period of four weeks.
      • ‘I've always wondered, but assumed it was because one week is a quarter of a lunar month.’
      • ‘A normal full-term pregnancy lasts 40 weeks or 10 lunar months.’


lunar month

/ˈlunər mənθ/