roughness vs rough water

roughness and rough water both are nouns.

Word	Noun	Adjective	Verb	Adverb
roughness	Yes	No	No	No
rough water	Yes	No	No	No

As nouns, roughness and rough water are synonyms defined as:

roughness and rough water: used of the sea during inclement or stormy weather

Other synonyms of roughness include choppiness.

roughness (noun)	rough water (noun)
harsh or severe speech or behavior	used of the sea during inclement or stormy weather
a texture of a surface or edge that is not smooth but is irregular and uneven
the quality of being harsh or rough or grating to the senses
an unpolished unrefined quality
the formation of small pits in a surface as a consequence of corrosion
used of the sea during inclement or stormy weather
rowdy behavior