king vs Gustavus I

king and Gustavus I both are nouns.

Word	Noun	Adjective	Verb	Adverb
king	Yes	No	No	No
Gustavus I	Yes	No	No	No

king (noun)	Gustavus I (noun)
(chess) the weakest but the most important piece	king of Sweden who established Lutheranism as the state religion (1496-1560)
one of the four playing cards in a deck bearing the picture of a king
a checker that has been moved to the opponent's first row where it is promoted to a piece that is free to move either forward or backward
a male sovereign; ruler of a kingdom
a very wealthy or powerful businessman
a male competitor who holds a preeminent position
the husband or widower of a queen
preeminence in a particular category or group or field