President β Republic titles
The most common title for the person who represents a nation in a republic, chosen through election by the people (or by a parliament or electoral college). The actual degree of power varies enormously by country, ranging from "presidential systems," in which the president wields strong executive authority, to "symbolic presidents in parliamentary systems," whose role is closer to ceremonial. Representative examples: the United States, France, South Korea, and many other republics.
Prime Minister β Republic titles
The title held by the person who serves as the de facto head of the executive branch in a parliamentary system. In constitutional monarchies or republics with a ceremonial president, the roles of head of state (monarch or president) and head of government (prime minister) are often divided between two different people. Representative examples: the United Kingdom, Japan, Germany (where the prime minister is called "Bundeskanzler").
King / Queen β Monarchy titles
The traditional title in a monarchy, where the throne is passed down hereditarily. In most constitutional monarchies today, the role is more symbolic of national unity than one of real power, with actual governance handled by the prime minister and parliament. Representative examples: the United Kingdom, Spain, Thailand, and Saudi Arabia (where the king also holds real political power).
Emperor β Monarchy titles
A title originating from a rank considered higher than "king," historically given to a ruler presiding over multiple peoples or regions. Today, Japan is the only country that officially uses the title "Emperor," and under Japan's constitution, it is a symbolic position with no political power.
Sultan / Emir β Monarchy titles
Monarchical titles used in the Islamic cultural sphere: "sultan" was originally a title for a ruler governing a vast territory, as in the Ottoman Empire, while "emir" was a title for the ruler of a relatively smaller principality. A key difference from European royal families is that holders of these titles today still often hold genuine governing authority over their state. Representative examples: Brunei (Sultan), Qatar and Kuwait (Emir), the United Arab Emirates (one of the seven emirates' rulers, or emirs, also serves as president).
Pope β Other distinctive titles
Serves simultaneously as the head of the Catholic Church and the head of state of Vatican City, the world's smallest independent country. The position is held for life and is filled through a conclave (election) of the College of Cardinals. Representative example: Vatican City.
Chairman / State Chairman β Other distinctive titles
A head-of-state title commonly used in socialist-system countries. A notable feature is that it often comes bundled together with the top position within the ruling party β such as "supreme leader" or "general secretary" β with the holder overseeing state affairs overall. Representative examples: China (State Chairman), North Korea (Chairman of the State Affairs Commission).