The plural of the noun principal is principals (loan values, school heads, or those with a proprietary interest).
The plural of the homophone principle is principles.
The plural of principality is principalities.
In the Bible 'principality' means a kingdom or empire with a ruler. It covers all sizes from a large country to a small city state. In the plural it means the rulers of the world.
I'm looking for the main library in this principality.
Principality of Andorra
Principality of Regensburg was created in 1803.
Principality of Orange was created in 1163.
Principality of Orange ended in 1713.
Principality of Guria ended in 1829.
Principality of Göttingen was created in 1279.
Principality of Serbia was created in 1817.
Principality of Serbia ended in 1882.
Principality of Trubetsk ended in 1566.
Principality of Beloozero was created in 1238.