send vs mail

send is not a noun while mail is a noun.

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

As verbs, send and mail are synonyms defined as:

Other synonyms of send include post.

As verbs, mail is a hyponym of send; that is, mail is a word with a more specific, narrower meaning than send:

send: to cause or order to be taken, directed, or transmitted to another place
mail: send via the postal service

Other hyponyms of send include send in, mail out, get off.

send (noun)	mail (noun)
	(Middle Ages) flexible armor made of interlinked metal rings
	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

send (verb)	mail (verb)
cause to be directed or transmitted to another place	cause to be directed or transmitted to another place
transfer	send via the postal service
broadcast over the airwaves, as in radio or television
assign to a station
to cause or order to be taken, directed, or transmitted to another place
transport commercially
cause to go somewhere
cause to be admitted; of persons to an institution