Hexapla
Hexapla (Ancient Greek: Ἑξαπλᾶ, "sixfold") is the term for an edition of the Bible in six versions. It is an immense and complex word-for-word comparison of the Greek Septuagint with the original Hebrew Scriptures, and other Greek translations. The term especially and generally applies to the edition of the Old Testament compiled by the theologian and scholar Origen, sometime before the year 240 CE, which placed side by side:
Hebrew
Secunda – Hebrew transliterated into Greek characters
Aquila of Sinope
Symmachus the Ebionite
A recension of the Septuagint, with (1) interpolations to indicate where the Hebrew is not represented in the Septuagint—these are taken mainly from Theodotion's text and marked with asterisks, and (2) indications, using signs called obeloi (singular: obelus), of where words, phrases, or occasionally larger sections in the Septuagint do not reflect any underlying Hebrew.
Theodotion
Origen's eclectic recension of the Septuagint had a significant influence on the Old Testament text in several important manuscripts, such as the Codex Sinaiticus. The original work, which is said to have had about 6000 pages in 15 volumes and which probably only ever existed in a single complete copy, seems to have been stored in the library of the bishops of Caesarea for some centuries, but it was destroyed during the Muslim invasion of the year 638 at the latest. The subsisting fragments of partial copies have been collected in several editions, for example that of Frederick Field (1875).