The Christian varieties are often called Modern Syriac (or Neo-Syriac, particularly when referring to their literature), being deeply influenced by the old literary and liturgical language, the Classical Syriac. However, they also have roots in numerous, previously unwritten, local Aramaic varieties, and are not purely the direct descendants of the language of Ephrem the Syrian. The varieties are not all mutually intelligible. The principal Christian varieties are Assyrian Neo-Aramaic and Chaldean Neo-Aramaic, both belonging to the group of Northeastern Neo-Aramaic languages.