The darkness or shadow that happens when something blocks the light.
Shadiness can be scary or mysterious, like in a spooky story.
Examples:
The tree gives shadiness to the yard.
She sits in the shadiness to cool off.
The shadiness of the building makes it hard to see inside.
The cat likes to hide in the shadiness under the porch.
The deep shadiness of the forest made it hard to see anything.
The shadiness of the cave made it a good place to hide.