Definition of regal by Cambridge Dictionary:
very special and suitable for a king or queen
Definition of royal by Cambridge Dictionary:
belonging or connected to a king or queen or a member of their family
"Such propaganda was significant at the time, since papal reform would soon be trying to damage regal imagery."
Essentially, regal is another adjective of royal. What is the difference if I use "royal" instead? And it seems like it is more restricted to use regal compared to royal. So in what circumstance is the word regal appropriate and suitable?