blank space vs margin

blank space and margin both are nouns.

Word	Noun	Adjective	Verb	Adverb
blank space	Yes	No	No	No
margin	Yes	No	No	No

As nouns, margin is a hyponym of blank space; that is, margin is a word with a more specific, narrower meaning than blank space:

Other hyponyms of blank space include indent, indentation, indention, indenture.

blank space (noun)	margin (noun)
a blank area	an amount beyond the minimum necessary
	a permissible difference; allowing some freedom to move within limits
	the blank space that surrounds the text on a page
	the amount of collateral a customer deposits with a broker when borrowing from the broker to buy securities
	(finance) the net sales minus the cost of goods and services sold
	the boundary line or the area immediately inside the boundary