king vs oil tycoon

king and oil tycoon both are nouns.

Word	Noun	Adjective	Verb	Adverb
king	Yes	No	No	No
oil tycoon	Yes	No	No	No

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

king (noun)	oil tycoon (noun)
(chess) the weakest but the most important piece	a powerful person in the oil business
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