Sirius vs Dog Star

Sirius and Dog Star both are nouns.

Word	Noun	Adjective	Verb	Adverb
Sirius	Yes	No	No	No
Dog Star	Yes	No	No	No

As nouns, Sirius and Dog Star are synonyms defined as:

Other synonyms of Sirius include Canicula, Sothis.

Sirius (noun)	Dog Star (noun)
the brightest star in the sky; in Canis Major	the brightest star in the sky; in Canis Major