horizon

1. (figuratively) The range or limit of one's knowledge, experience or interest; a boundary or threshold.Examples: "Some students take a gap year after finishing high school to broaden their horizons."; "With clinical researchers hard at work, a new treatment is on the horizon."; "It is because theirs has become the only explicit general philosophy of social policy held by a large group, the only system or theory which raises new problems and opens new horizons, that they have succeeded in inspiring the imagination of the intellectual."figuratively

2. (geology) A specific layer of soil, or stratum

3. (archaeology, chiefly US) A cultural sub-period or level within a more encompassing time period.US

4. (computer chess) The point at which a computer chess algorithm stops searching for further moves.