treadle vs accelerator

treadle and accelerator both are nouns.

Word	Noun	Adjective	Verb	Adverb
treadle	Yes	No	Yes	No
accelerator	Yes	No	No	No

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

treadle (noun)	accelerator (noun)
a lever that is operated with the foot	a valve that regulates the supply of fuel to the engine
	a scientific instrument that increases the kinetic energy of charged particles
	a pedal that controls the throttle valve
	(chemistry) a substance that initiates or accelerates a chemical reaction without itself being affected

treadle (verb)	accelerator (verb)
operate (machinery) by a treadle
tread over