Erythraean Sea (Gr. red, ruddy), in ancient geography, originally the name of the whole expanse of sea between Africa on the S. W., Arabia on the N. W., Gedrosia on the N., and India on the N. E., including the two great gulfs, the Arabian and the Persian. In this wider sense the term seems to have been used by Herodotus, who designates by it both the Indian ocean, of the shape of which he was ignorant, and the Persian gulf, distinguishing the Red sea, the yam suf or weedy sea of the Hebrews, which he calls the Arabian gulf. The term (southern sea) appears in some passages of the same historian as identical with the Erythraean, in others as designating the more distant and less known region of the latter. Later and better informed geographers, distinguishing the separate parts of the sea, applied to its main body the name of Indian ocean, and to its great gulfs the names of Persian and Arabian, while the term Erythraean sea (Lat. Mare Rubrum) was variously used by different writers until it became confined to the Arabian gulf. The sea is supposed by some to have derived its name from the Phoenicians (Gr. red), who according to Herodotus originally dwelt on its shores; and by others from the red or purple hues imparted by coral reefs to the waters of the strait which connects the Red sea proper with the Indian ocean.