drainage area vs river basin

drainage area and river basin both are nouns.

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

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

drainage area and river basin: 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 drainage area include basin, catchment area, catchment basin, drainage basin, watershed.

drainage area (noun)	river basin (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