Commissioner (noun)

1. A person appointed to oversee a particular function or area of public policy.
2. An official of a government or administrative body who has the authority to make decisions or recommendations.

Origin:

Late middle english: from old french commissiounaire, from medieval latin commissarius, from latin committere "commit".

Examples:

1. The commissioner of police was present at the crime scene.
2. The commissioner was appointed to investigate the incident.
3. The city commissioner is responsible for overseeing the department of parks and recreation.
4. The commissioner was in charge of the commission investigating police misconduct.
5. The commissioner announced that the commission had completed its work.