Sothis vs Dog Star

Sothis and Dog Star both are nouns.

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

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

Other synonyms of Sothis include Canicula, Sirius.

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