You may have heard a pastor make a reference to the Septuagint or seen it written in a commentary somewhere. You may have also seen references to LXX in books and wondered what it meant (large extra extra?). There is nothing magical or mysterious about the Septuagint but it is an important part of biblical history.
In short, the Septuagint is an ancient Greek translation of the Old Testament. The word has no special Bible meaning but in fact is simply the Greek word for seventy which is a reference to the seventy scholars who worked on the translation. LXX is the Roman/Greek number of 70 which is why it is often written that way – because it’s way easier to type LXX than Septuagint several times in an article.
Now, you’re probably wondering why an ancient translation of the Old Testament matters at all today. However it has not only historical significance but modern importance as well. For the ancient significance, when the Israelites were carried off into exile in Babylon, they ended up losing their Hebrew language. Half of the book of Daniel and the books of Ezra and Nehemiah are actually written in Aramaic instead of Hebrew.
When the exiles returned to Jerusalem and rebuilt the city and temple they had a bunch of scriptures that most of the people could no longer read because they didn’t speak Hebrew. Eventually the Old Testament was translated into Greek which is the common language of Jesus’ day and the language that the New Testament was written in.
The Septuagint is important today because it helps modern translators understand the Old Testament. When they encounter a Hebrew word that they are uncertain of, they have the benefit of looking at the LXX and seeing how those ancient translators interpreted the word. Sometimes it is translated as a Greek word that is also unfamiliar but sometimes they translated it into a word that the scholars understand well. All of this helps our modern English translations.
Finally, you might be wondering “why aren’t they done translating these texts if they’re so ancient?” The truth is that we are still finding ancient texts that are constantly bettering our understanding of the Bible and the languages that they were written in. For instance, the Dead Sea scrolls were discovered in Qumran over 60 years (unearthed between 1946 and 1956) and scholars are still learning from these pieces of history decades after their discovery!