indention vs blank space

indention and blank space both are nouns.

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

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

indention: the space left between the margin and the start of an indented line
blank space: a blank area

Other hypernyms of indention include place, space.

indention (noun)	blank space (noun)
the space left between the margin and the start of an indented line	a blank area