Crowned head and Rex

Crowned head noun - A nation's ruler or head of state usually by hereditary right.

Rex and crowned head are semantically related in ruler topic. In some cases you can use "Rex" instead a noun phrase "Crowned head", when it comes to topics like historically.

Rex noun - A male sovereign; ruler of a kingdom.

Crowned head and rex are semantically related in ruler topic. Sometimes you can use "Crowned head" instead a noun "Rex", if it concerns topics such as historically.