\begin{definition}[Definition:Phase of Moon]
The '''phase of the Moon''' is its apparent shape when viewed in the night sky of Earth.
This shape is dependent upon the position of the Moon with respect to the Sun and Earth.
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When the Moon is between the Sun and Earth, the sunlit side faces more or less away from Earth, and so less than half of it can be seen lit up.
When Earth is between the Sun and the Moon, the sunlit side faces more or less away towards Earth, and so more than half of it can be seen lit up.
When the Moon is directly between the Sun and Earth, the sunlit side is facing completely away from Earth, and in normal conditions cannot be seen.
This is the '''phase''' known as '''new moon'''.
When Earth is directly between the Sun and the Moon, the sunlit side is facing completely towards Earth, and in normal conditions appears as a brign disk.
This is the '''phase''' known as '''full moon'''.
At the point half way between new moon and full moon, the '''phase''' is known as '''first quarter'''.
At the point half way between full moon and new moon, the '''phase''' is known as '''last quarter'''.
Category:Definitions/Astronomy
\end{definition}