What is Month?

Month definition and meaning on Dictionary terms:
Also called calendar month. any of the twelve parts, as January or February, into which the calendar year is divided.
the time from any day of one calendar month to the corresponding day of the next.
a period of four weeks or 30 days.
Also called solar month. one-twelfth of a solar or tropical year.
Also called lunar month. the period of a complete revolution of the moon around the earth, as the period between successive new moons (synodic month), equal to 29.531 days, or the period between successive conjunctions with a star (sidereal month), equal to 27.322 days, or the period between successive perigees (anomalistic month), equal to 27.555 days, or the period between successive similar nodes (nodical month or draconic month), equal to 27.212 days.
an unusually long period of time of indefinite length: I haven’t seen him for months.