fryer vs donut machine

fryer and donut machine both are nouns.

Word	Noun	Adjective	Verb	Adverb
fryer	Yes	No	No	No
donut machine	Yes	No	No	No

As nouns, donut machine is a hyponym of fryer; that is, donut machine is a word with a more specific, narrower meaning than fryer:

fryer: A kitchen appliance for deep frying; its size depends on intended use.
donut machine: a machine used to fry large quantities of doughnuts at once.

Other hyponyms of fryer include donut fryer, doughnut fryer, doughnut machine.

fryer (noun)	donut machine (noun)
A kitchen appliance for deep frying; its size depends on intended use.	a machine used to fry large quantities of doughnuts at once.
flesh of a medium-sized young chicken suitable for frying