Dog Star vs Sothis

Dog Star and Sothis both are nouns.

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

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

Other synonyms of Dog Star include Canicula, Sirius.

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