governor vs flywheel

governor and flywheel both are nouns.

Word	Noun	Adjective	Verb	Adverb
governor	Yes	No	No	No
flywheel	Yes	No	No	No

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

governor: a control that maintains a steady speed in a machine (as by controlling the supply of fuel)
flywheel: regulator consisting of a heavy wheel that stores kinetic energy and smooths the operation of a reciprocating engine

Other hyponyms of governor include timer.

governor (noun)	flywheel (noun)
a control that maintains a steady speed in a machine (as by controlling the supply of fuel)	regulator consisting of a heavy wheel that stores kinetic energy and smooths the operation of a reciprocating engine
the head of a state government