add vs adder

add is not a noun while adder is a noun.

Word	Noun	Adjective	Verb	Adverb
add	No	No	Yes	No
adder	Yes	No	No	No

add (noun)	adder (noun)
	small terrestrial viper common in northern Eurasia
	a machine that adds numbers
	a person who adds numbers

add (verb)	adder (verb)
make an addition (to); join or combine or unite with others; increase the quality, quantity, size or scope of
make an addition by combining numbers
determine the sum of
state or say further
bestow a quality on
constitute an addition