king vs King of France

king and King of France both are nouns.

Word	Noun	Adjective	Verb	Adverb
king	Yes	No	No	No
King of France	Yes	No	No	No

As nouns, King of France is a hyponym of king; that is, King of France is a word with a more specific, narrower meaning than king:

Other hyponyms of king include King of England, King of Great Britain, King of the Germans.

king (noun)	King of France (noun)
(chess) the weakest but the most important piece	the sovereign ruler of France
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