pipefitting vs reducer

pipefitting and reducer both are nouns.

Word	Noun	Adjective	Verb	Adverb
pipefitting	Yes	No	No	No
reducer	Yes	No	No	No

As nouns, reducer is a hyponym of pipefitting; that is, reducer is a word with a more specific, narrower meaning than pipefitting:

pipefitting: fitting consisting of threaded pieces of pipe for joining pipes together
reducer: pipefitting that joins two pipes of different diameter

pipefitting (noun)	reducer (noun)
fitting consisting of threaded pieces of pipe for joining pipes together	pipefitting that joins two pipes of different diameter
	a substance capable of bringing about the reduction of another substance as it itself is oxidized; used in photography to lessen the density of a negative or print by oxidizing some of the loose silver