airmail vs mail

airmail and mail both are nouns.

Word	Noun	Adjective	Verb	Adverb
airmail	Yes	No	Yes	No
mail	Yes	No	Yes	No

As nouns, mail is a hypernym of airmail; that is, mail is a word with a broader meaning than airmail:

Other hypernyms of airmail include mail service, post, postal service.

As nouns, mail is a hypernym of airmail; that is, mail is a word with a broader meaning than airmail:

airmail: letters and packages that are transported by aircraft
mail: the bags of letters and packages that are transported by the postal service

As verbs, mail is a hypernym of airmail; that is, mail is a word with a broader meaning than airmail:

Other hypernyms of airmail include post, send.

airmail (noun)	mail (noun)
a system of conveying mail by aircraft	(Middle Ages) flexible armor made of interlinked metal rings
letters and packages that are transported by aircraft	a conveyance that transports the letters and packages that are conveyed by the postal system
	the system whereby messages are transmitted via the post office
	the bags of letters and packages that are transported by the postal service
	any particular collection of letters or packages that is delivered

airmail (verb)	mail (verb)
send or transport by airmail	cause to be directed or transmitted to another place
	send via the postal service