Monarch (noun)

1. A sovereign head of state, especially a king, queen, or emperor.
2. A ruler or sovereign of a particular country or empire.

Origin:

Late middle english (denoting a ruler of an independent state): via old french from latin monarquus, from greek monarkhēs, from monos "single" + arkhē "rule".

Examples:

1. The monarch took a keen interest in the development of the country's economy.
2. Monarchs from various countries attended the coronation ceremony.
3. Queen Elizabeth II is the current monarch of England.
4. The monarch's powers are limited by the country's constitution.
5. The monarch gave a speech to the gathered crowd in front of the palace.