label vs know as

label is a noun but know as is not a noun.

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

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

Other hyponyms of label include call, address, direct, be known as, call, name, brand, denounce, mark, stigmatise, stigmatize.

label (noun)	know as (noun)
an identifying or descriptive marker that is attached to an object
a brief description given for purposes of identification
trade name of a company that produces musical recordings
a radioactive isotope that is used in a compound in order to trace the mechanism of a chemical reaction

label (verb)	know as (verb)
distinguish (an element or atom) by using a radioactive isotope or an isotope of unusual mass for tracing through chemical reactions	look on as or consider
distinguish (as a compound or molecule) by introducing a labeled atom	assign a specified (usually proper) name to
assign a label to; designate with a label
pronounce judgment on
attach a tag or label to