Concise Bible Dictionary:

This word occurs 2 Kings 18:26; Ezra 4:7; and Isaiah 36:11, where it is translated “the Syrian language” or “tongue”; also in Daniel 2:4, where it is “Syriack.” Aramaic is the language of Aram, and embraces the language of Chaldee and that of Syria. Mesopotamia, Babylonia and Syria were its proper home. The first time we meet with it in scripture is in Genesis 31:47, where Laban called the heap of witness “Jegar-sahadutha,” which is Chaldee; whereas Jacob gave it a Hebrew name, “Galeed.” In 2 Kings 18:26 and Isaiah 36:11 The heads of the people asked Rab-shakeh to speak to them in Aramaic that the uneducated might not understand what was said. In Ezra 4:7 the letter sent to Artaxerxes was written in Aramaic, and interpreted in Aramaic, that is, the copy of the letter and what follows as far as Ezra 6:18 is in that language and not in Hebrew. So also is Ezra 7:12-26.
In Daniel 2:4 the Chaldeans spoke to the king in Aramaic, the popular language of Babylon, and what follows to the end of Daniel 7 is in that language, though commonly called Chaldee. This must not be confounded with the “learning and the tongue of the Chaldeans” in Daniel 1:4, which is the Aryan dialect and literature of the Chaldeans, and probably the ordinary language which Daniel spoke in the court of Babylon. Jeremiah 10:11 is a verse in Aramaic.
This language differs from the Hebrew in that it avoids the sibilants. Where the Hebrew has ז z, ש sh, צ tz, the Aramaic has ? d, ? n, ? th, and ? t. Letters of the same organ are also interchanged, the Aramaic choosing the rough harder sounds. The latter has fewer vowels, with many variations in the conjugation of verbs, etc.
When the ten tribes were carried away, the colonists, who took their place, brought the Aramaic language with them. The Jews also who returned from Babylon brought many words of the same language. And, though it doubtless underwent various changes, this was the language commonly spoken in Palestine when our Lord was on earth, and is the language called HEBREW in the New Testament, and is the same as the Chaldee of the Targums. In the ninth century the language in Palestine gave way to the Arabic, and now Aramaic is a living tongue only among the Syrian Christians in the district around Mosul.