A commissioner is someone appointed to lead and oversee an important organization or department.

You'll often hear about commissioners running professional sports leagues. The Commissioner of Major League Baseball, for example, makes major decisions about rules, schedules, and disputes between teams. When a controversy erupts or a big change needs to happen, the commissioner has the final say.

Cities and counties have commissioners too. A police commissioner heads the police department, while a parks commissioner manages all the public parks and recreation programs. These commissioners develop policies, manage budgets, and answer to the public about how well their departments are running.

The word suggests authority and responsibility together. A commissioner is accountable for major decisions that affect many people. When a school board appoints a commissioner of education for a district, that person becomes responsible for thousands of students' learning.

In British English, a High Commissioner serves as an ambassador between Commonwealth countries, which is a different meaning of the same word.