robin vs American robin

robin and American robin both are nouns.

Word	Noun	Adjective	Verb	Adverb
robin	Yes	No	No	No
American robin	Yes	No	No	No

As nouns, robin and American robin are synonyms defined as:

robin and American robin: large American thrush having a rust-red breast and abdomen

Other synonyms of robin include Turdus migratorius.

robin (noun)	American robin (noun)
large American thrush having a rust-red breast and abdomen	large American thrush having a rust-red breast and abdomen
small Old World songbird with a reddish breast