A period into which a year is divided, historically based on the phases of the moon. / A period of 30 days, 31 days, or some alternation thereof.

plural of month

(obsolete) A woman's period; menstrual discharge.

plural of monthful

A quantity that lasts or occurs throughout a month.

(idiomatic) During every month; continuously.

(idiomatic, informal) A very long time; a period regarded as too long.

a month of approximately 29.53 days, measured from a lunar phase until the return of that same phase. The long-term average duration is 29.530 588 days (29 d 12 h 44 min 2.8 s), or about 29 ½ days.

a period from one new moon until the next. / a synodic month of approximately 29.53 days, measured from a lunar phase until the return of that same phase.

A month with an extra day in a leap year.