- Latin for shadow. Has two main uses among astronomers – for the dark central zone of a sunspot and for the dark centre part of the Earth’s or Moon’s shadow at an eclipse.
- A dark area, such as that of a shadow, which is blocked from light rays emanating from a given source. Also, the darkest area of such a shadow.
- A dark area arising from the shadow cast by a celestial body, such as the sun or moon, during an eclipse. Also, the darkest area of such a shadow.