benchmark vs bench mark

benchmark and bench mark both are nouns.

Word	Noun	Adjective	Verb	Adverb
benchmark	Yes	No	No	No
bench mark	Yes	No	No	No

As nouns, benchmark and bench mark are synonyms defined as:

benchmark and bench mark: a surveyor's mark on a permanent object of predetermined position and elevation used as a reference point

benchmark (noun)	bench mark (noun)
a standard by which something can be measured or judged	a surveyor's mark on a permanent object of predetermined position and elevation used as a reference point
a surveyor's mark on a permanent object of predetermined position and elevation used as a reference point