lighter vs fuel

lighter and fuel both are nouns.

Word	Noun	Adjective	Verb	Adverb
lighter	Yes	No	Yes	No
fuel	Yes	No	Yes	No

As nouns, fuel is a hypernym of lighter; that is, fuel is a word with a broader meaning than lighter:

lighter (noun)	fuel (noun)
a device for lighting or igniting fuel or charges or fires	a substance that can be consumed to produce energy
a flatbottom boat for carrying heavy loads (especially on canals)
a substance used to ignite or kindle a fire

lighter (verb)	fuel (verb)
transport in a flatbottom boat	stimulate
	provide with a combustible substance that provides energy
	provide with fuel
	take in fuel, as of a ship