Eridanus is a Zodiacal constellation otherwise known as the River. It is one of the 48 Greek constellations originally described by the 2nd century astronomer Claudius Ptolemy (Wikipedia). Eridanus remains one of the 88 modern constellations defined by the International Astronomical Union (Wikipedia).
Eridanus (abbrev. = Eri; genitive = Eridani) covers 1138 square degrees or 2.76% of the celestial sphere making it the 6th largest constellation. It contains 194 stars brighter than apparent magnitude 6.5, the brightest star being Achernar.