Watershed (noun)

1. A region or area of land that drains water into a particular body of water, such as a river, lake, or ocean.
2. A significant event or point that marks a turning point in a particular situation or development.

Origin:

From the land that drains water into a particular body of water.

Examples:

1. The watershed of the river was home to many different species of fish.
2. The watershed area was protected from development to preserve the water quality.
3. This election is a watershed moment in the country's history.
4. The new policy is a watershed in the company's approach to sustainability.
5. The invention was a watershed in the field of medicine.