 After the Persian conquest the River Maeander was regarded as its southern boundary, and during imperial Roman times Lydia comprised the country between Mysia and Caria on the one side and Phrygia and the Aegean Sea on the other.The Lydian language was an Indo-European language in the Anatolian language family, related to Luwian and Hittite.Due to its fragmentary attestation, the meanings of many words are unknown but much of the grammar has been determined.