There are several definitions of Black Moon. It can be the third New Moon in an astronomical season with four New Moons or the second New Moon in the same calendar month.

Black Moon is not a well known term in the astronomy world. In recent years, the term has been made popular by astrologers and followers of the Wiccan religion.
No Single Definition
There is no single accepted definition of a Black Moon. The term has been commonly used to refer to any of the following phenomena associated with the New Moon:
- Second New Moon in a calendar month: These Black Moons occur relatively often – once every 2.5 years.
- Third new moon in a season of four New Moons: Astronomers divide a year into fourseasons – spring, summer, fall (autumn)…
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