petrol vs hydrocarbon

petrol and hydrocarbon both are nouns.

Word	Noun	Adjective	Verb	Adverb
petrol	Yes	No	No	No
hydrocarbon	Yes	No	No	No

As nouns, hydrocarbon is a hypernym of petrol; that is, hydrocarbon is a word with a broader meaning than petrol:

petrol: a volatile flammable mixture of hydrocarbons (hexane and heptane and octane etc.) derived from petroleum; used mainly as a fuel in internal-combustion engines
hydrocarbon: an organic compound containing only carbon and hydrogen

Other hypernyms of petrol include fuel.

petrol (noun)	hydrocarbon (noun)
a volatile flammable mixture of hydrocarbons (hexane and heptane and octane etc.) derived from petroleum; used mainly as a fuel in internal-combustion engines	an organic compound containing only carbon and hydrogen