stoppage vs vapour lock

stoppage and vapour lock both are nouns.

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

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

stoppage: an obstruction in a pipe or tube
vapour 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, vapor lock.

stoppage (noun)	vapour 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