stoppage vs vapor lock

stoppage and vapor lock both are nouns.

Word	Noun	Adjective	Verb	Adverb
stoppage	Yes	No	No	No
vapor lock	Yes	No	No	No

As nouns, vapor lock is a hyponym of stoppage; that is, vapor lock is a word with a more specific, narrower meaning than stoppage:

stoppage: an obstruction in a pipe or tube
vapor lock: a stoppage in a pipeline caused by gas bubbles (especially a stoppage that develops in hot weather in an internal-combustion engine when fuel in the gas line boils and forms bubbles that block the flow of gasoline to the carburetor)

Other hyponyms of stoppage include breech closer, breechblock, plug, stopper, stopple, vapour lock.

stoppage (noun)	vapor lock (noun)
the act of stopping something	a stoppage in a pipeline caused by gas bubbles (especially a stoppage that develops in hot weather in an internal-combustion engine when fuel in the gas line boils and forms bubbles that block the flow of gasoline to the carburetor)
an obstruction in a pipe or tube
the state of inactivity following an interruption