waning moon

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the moon at any time after full moon and before new moon (so called because its illuminated area is decreasing).


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Also called old moon.
Compare waxing moon.

Origin of waning moon

before 1000; Middle English; Old English

Words nearby waning moon

Dictionary.com Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2022


What is a waning moon?

The moon is called a waning moon when it is in the phase in which its visible surface area is getting smaller. A waning moon occurs between a full moon (when the visible surface is fully round and lit up) and a new moon (when the surface that faces Earth is completely covered in shadow).

To wane is to decrease in some way. A moon is any natural satellite that orbits a planet, and the moon is Earth’s only natural satellite.

While the moon could be said to be a waning moon at any time between a full moon and a new moon, a waning moon is frequently depicted as a crescent shape.

Waning moon vs. waxing moon

Early astronomers were using a form of the term waning moon more than 1,000 years ago! They noticed the same thing you’ve probably noticed: the side of the moon that always faces Earth gets covered by Earth’s shadow in regular intervals (called phases). These phases occur over a period of about 29 days, called the lunar phase cycle.

Depending on where the moon is in relation to the Earth and the sun, Earth’s shadow changes the “shape” of the moon’s surface that is visible to us. When the moon is directly between Earth and the sun, the side facing Earth receives no sunlight and is therefore completely dark. This is called a new moon. As the moon continues to rotate around Earth, its visible side receives more and more sunlight. This phase is called a waxing moon. When its visible side is fully illuminated, it is called a full moon. After a full moon, the visible side of the moon begins to have less and less sunlight shining on it and will slowly appear to shrink into a crescent shape. This period of the lunar phase cycle is called a waning moon.

During the waning moon phase, the moon will go from a full moon to a moon partially covered in shadow, called a waning gibbous. As the light decreases, the moon will appear as a half moon, called a third quarter moon. A third quarter moon will continue to be covered in more shadow until it resembles a crescent shape, called a waning crescent. Eventually, it will be covered entirely in shadow and become a new moon again.

Did you know ... ?

While a waning moon is often depicted as a moon getting darker from right to left, this is only true in the Northern Hemisphere. Because Earth is round, the appearance of the moon is inverted (“upside down”) in the Southern Hemisphere, where a waning moon appears to shrink from left to right.

What are real-life examples of waning moon?

This video shows how the moon goes through the lunar phase cycle:

The moon and its many phases are often a source of inspiration for those gazing at the night sky.


What other words are related to waning moon?

Quiz yourself!

True or False?

A waning moon is the phase between a new moon and a full moon, in which the amount of light on the surface is increasing.

How to use waning moon in a sentence