What word am I thinking of?

At the office I had to explain the concept of “Diplomatic Immunity.” That led to “Sovereignty.”

That led me another half-remembered word that means something like “Sovereignty.” It begins with a S, it ends with a Y and has a Z in it somewhere. Any thoughts?

supremacy … nope, supreme power … nope, sway … nope …

Surengency? Suregengzy? Fiddlesticks!

suzerainty ???

We have a winner!

Many thanks. Let me print out the definition.

Google’s definition.