The state of being unknown; a thing that is unknown.
The quality of being difficult to understand; a thing that is difficult to understand.
Darkness; the absence of light.
A bulge: something that bulges out or is protuberant or projects from a form.
The state of being prominent: widely known or eminent.
Autonomous height; relative height or prime factor; a concept used in the categorization of hills and mountains.
A gaseous projection, often loop-shaped, springing from the surface of the Sun or a star.
Relative importance.