Monarca vs. sovrano
The Italian words 'monarca' and 'sovrano' both refer to rulers, but they have subtle differences in usage and connotation.
Monarca
'Monarca' specifically refers to a monarch, typically a king or queen who rules a kingdom or empire.
Il monarca britannico ha un ruolo principalmente cerimoniale.
(The British monarch has a primarily ceremonial role.)
La successione al trono determina chi sarà il prossimo monarca.
(The succession to the throne determines who will be the next monarch.)
Sovrano
'Sovrano' is a broader term that can mean sovereign, ruler, or supreme authority, not limited to monarchs.
In una democrazia, il popolo è considerato il sovrano.
(In a democracy, the people are considered the sovereign.)
Il presidente agisce come sovrano capo di stato nella repubblica.
(The president acts as the sovereign head of state in the republic.)
Summary
While 'monarca' specifically refers to a monarch in a traditional sense, 'sovrano' is a more versatile term that can apply to various forms of supreme authority, including monarchs but also extending to other types of rulers or even the concept of popular sovereignty.