A more thorough explanation:

Definition: A league is a covenant or agreement made by nations, groups, or individuals to promote common interests or ensure mutual protection. It can also refer to an alliance or association of nations, groups, or individuals formed by such a covenant. Additionally, a league can be a unit of distance, usually measuring about three miles (especially in nautical terms).

• The United Nations is a league of nations that work together to promote peace and security around the world.
• The National Football League (NFL) is an association of American football teams that compete against each other for a championship title.
• In ancient Greece, a league referred to a group of city-states that formed an alliance for mutual protection and defense.
• A nautical league is a unit of distance used in navigation, equal to three nautical miles.

These examples illustrate how a league can refer to different types of agreements or associations, whether it be for political, sports, or navigational purposes. In each case, the league is formed to achieve a common goal or provide mutual benefits to its members.