string up vs add

string up and add both are verbs.

Word	Noun	Adjective	Verb	Adverb
string up	No	No	Yes	No
add	No	No	Yes	No

As verbs, add is a hypernym of string up; that is, add is a word with a broader meaning than string up:

string up: add as if on a string
add: make an addition (to); join or combine or unite with others; increase the quality, quantity, size or scope of

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