SOURCE.WIKIPEDIA

Suzerainty (pronounced /ˈsjuːzərənti/RP or /ˈsjuːzəreɪnti/RP) (/ˈsuːzərənti/ GA) is a situation in which a region or people is a tributary to a more powerful entity which allows the tributary some limited domestic autonomy to control its foreign affairs. The more powerful entity in the suzerainty relationship, or the head of state of that more powerful entity, is called a suzerain. The term suzerainty was originally used to describe the relationship between the Ottoman Empire and its surrounding regions. It differs from sovereignty in that the tributary has some (limited) self-rule. A suzerain can also mean a feudal lord, to whom vassals must pay tribute.

Although it is a concept which has existed in a number of historical empires, it is a concept that is very difficult to describe using 20th- or 21st-century theories of international law, in which sovereignty either exists or does not. While a sovereign nation can agree by treaty to become a protectorate of a stronger power, modern international law does not recognize any way of making this relationship compulsory on the weaker power.

The word is often spelled "suzerainity", though this has come to be considered incorrect.