margin vs blank space

margin and blank space both are nouns.

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

As nouns, blank space is a hypernym of margin; that is, blank space is a word with a broader meaning than margin:

Other hypernyms of margin include place, space.

margin (noun)	blank space (noun)
an amount beyond the minimum necessary	a blank area
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