river basin vs catchment area

river basin and catchment area both are nouns.

Word	Noun	Adjective	Verb	Adverb
river basin	Yes	No	No	No
catchment area	Yes	No	No	No

As nouns, river basin and catchment area are synonyms defined as:

river basin and catchment area: the entire geographical area drained by a river and its tributaries; an area characterized by all runoff being conveyed to the same outlet

Other synonyms of river basin include basin, catchment basin, drainage area, drainage basin, watershed.

river basin (noun)	catchment area (noun)
the entire geographical area drained by a river and its tributaries; an area characterized by all runoff being conveyed to the same outlet	the entire geographical area drained by a river and its tributaries; an area characterized by all runoff being conveyed to the same outlet