Umbra (noun)

1. The darkest part of a shadow, where the source of light is completely blocked.
2. The innermost and darkest part of a sunspot.
3. The dark central area of a lunar eclipse shadow.

Origin:

From latin umbra, meaning "shadow" or "shade".

Examples:

1. During a solar eclipse, the moon's umbra causes the total eclipse, while the penumbra causes a partial eclipse.
2. During the total solar eclipse, the sky goes dark in the umbra, while it remains partially lit in the penumbra.
3. The umbra of the sunspot is where the magnetic field is strongest and most disrupted.
4. The umbra is the central part of the lunar eclipse shadow that causes the total eclipse.
5. The umbra is the area of complete shadow in an eclipse, as opposed to the penumbra, which is the area of partial shadow.