space vs outer space

space and outer space both are nouns.

Word	Noun	Adjective	Verb	Adverb
space	Yes	No	Yes	No
outer space	Yes	No	No	No

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

Other hyponyms of space include absolute space, phase space, mathematical space, topological space, space.

As nouns, space and outer space are synonyms defined as:

space (noun)	outer space (noun)
the unlimited expanse in which everything is located	any location outside the Earth's atmosphere
(printing) a block of type without a raised letter; used for spacing between words or sentences
a blank character used to separate successive words in writing or printing
a blank area
one of the areas between or below or above the lines of a musical staff
an area reserved for some particular purpose
any location outside the Earth's atmosphere
an empty area (usually bounded in some way between things)
the interval between two times

space (verb)	outer space (verb)
place at intervals