know as vs tag

know as is not a noun while tag is a noun.

Word	Noun	Adjective	Verb	Adverb
know as	No	No	Yes	No
tag	Yes	No	Yes	No

As verbs, tag is a hyponym of know as; that is, tag is a word with a more specific, narrower meaning than know as:

Other hyponyms of know as include baptise, baptize, christen, refer, style, title, dub, nickname, rename, entitle, title, term.

know as (noun)	tag (noun)
	(sports) the act of touching a player in a game (which changes their status in the game)
	a game in which one child chases the others; the one who is caught becomes the next chaser
	a small piece of cloth
	a label written or printed on paper, cardboard, or plastic that is attached to something to indicate its owner, nature, price, etc.
	a label associated with something for the purpose of identification

know as (verb)	tag (verb)
look on as or consider	provide with a name or nickname
assign a specified (usually proper) name to	attach a tag or label to
	touch a player while he is holding the ball
	supply (blank verse or prose) with rhymes
	go after with the intent to catch