aqualung vs ventilator

aqualung and ventilator both are nouns.

Word	Noun	Adjective	Verb	Adverb
aqualung	Yes	No	No	No
ventilator	Yes	No	No	No

As nouns, ventilator is a hypernym of aqualung; that is, ventilator is a word with a broader meaning than aqualung:

aqualung: a device (trade name Aqua-Lung) that lets divers breathe under water; scuba is an acronym for self-contained underwater breathing apparatus
ventilator: a device that facilitates breathing in cases of respiratory failure

Other hypernyms of aqualung include breathing apparatus, breathing device, breathing machine.

aqualung (noun)	ventilator (noun)
a device (trade name Aqua-Lung) that lets divers breathe under water; scuba is an acronym for self-contained underwater breathing apparatus	a device (such as a fan) that introduces fresh air or expels foul air
	a device that facilitates breathing in cases of respiratory failure