What is the Septuagint?

As we continue our textual criticism series of posts which focus on the Tanakh, we know turn to the Septuagint.

What is the Septuagint (also know by the abbreviation LXX)?

Here's a good definiton:

The Septuagint (LXX) is the name commonly given in the West to the Koine Greek Alexandrine text of the Hebrew Bible (Tanakh/Old Testament) produced some time between the third to first century BC.

And another:

Septuagint (sometimes abbreviated LXX) is the name given to the Greek translation of the Jewish Scriptures. The Septuagint has its origin in Alexandria, Egypt and was translated between 300-200 BC. Widely used among Hellenistic Jews, this Greek translation was produced because many Jews spread throughout the empire were beginning to lose their Hebrew language. The process of translating the Hebrew to Greek also gave many non-Jews a glimpse into Judaism. According to an ancient document called the Letter of Aristeas, it is believed that 70 to 72 Jewish scholars were commissioned during the reign of Ptolemy Philadelphus to carry out the task of translation. The term “Septuagint” means seventy in Latin, and the text is so named to the credit of these 70 scholars.