The visible horizontal line or point (in all directions) that appears to connect the Earth to the sky.
The range or limit of one's knowledge, experience or interest; a boundary or threshold.
The range or limit of any dimension in which one exists.
A specific layer of soil or strata
A cultural sub-period or level within a more encompassing time period.
Any level line or surface.
The point at which a computer chess algorithm stops searching for further moves.