Regulator (noun)

1. A person or thing that regulates, especially a device in a machine that controls its speed or operation.
2. An official or organization responsible for overseeing and controlling specific activities or sectors, such as finance or utilities.

Origin:

Late 16th century (in the sense "one who regulates"): from latin regulat- "regulated", from the verb regulare, from regula "a ruler".

Examples:

1. The regulator ensured that the gas pressure was maintained at a constant level.
2. The financial regulators are responsible for ensuring that banks and other financial institutions operate within the law.
3. The environmental regulator sets standards for air and water pollution.
4. The regulator played a key role in the negotiation of the agreement between the two countries.
5. The regulator of the power grid was responsible for ensuring that electricity was distributed evenly across the country.