A half moon in the night sky looks like a perfectly round disc with exactly half of it illuminated and the other half in shadow.

Here's a more detailed description:

* Shape: It's a crescent shape, but a very wide one, resembling a slightly curved slice of pie or a half-circle.

* Illumination: The illuminated part is bright white, while the shadowed part is completely dark. The dividing line between the light and dark areas is very sharp and distinct.

* Position: The position of the half moon in the sky depends on its phase. A waxing half moon (growing) will be in the western sky after sunset, while a waning half moon (shrinking) will be in the eastern sky before sunrise.

You might find it helpful to imagine a perfectly round cookie with half of it covered in frosting. The frosting represents the illuminated part of the moon, while the plain cookie represents the shadowed part.