The word "anomoean" comes from Greek ἀ(ν)- 'not' and ὅμοιος 'similar': "different; dissimilar". In the 4th century, during the reign of Constantius II, this was the name by which the followers of Aëtius and Eunomius were distinguished as a theological party. The term "heterousian" derives from the Greek ἑτεροούσιος, heterooúsios, "differing in substance" from ἕτερος, héteros, "another" and οὐσία, ousía, "substance, being".