What happens to the moon after full moon day?

Explanation

**Step-by-Step Solution:**

1. **Understanding Full Moon Day**: The full moon day is when the entire face of the moon is illuminated and visible from Earth. This occurs when the Earth is positioned between the sun and the moon.

2. **Transition After Full Moon**: After the full moon day, the visible part of the moon begins to decrease. This phase is known as the waning phase.

3. **Waning Phase**: During the waning phase, the moon appears to shrink in size. This happens because the sunlight that illuminates the moon is gradually decreasing from our perspective on Earth.

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