Development of the Old Testament canon

The Old Testament is the first section of the two-part Christian Biblical canon; the second section is the New Testament. The Old Testament includes the books of the Hebrew Bible (Tanakh) or , and in various Christian denominations also includes deuterocanonical books. Orthodox Christians, Catholics and Protestants use different canons, which differ with respect to the texts that are included in the Old Testament.

Martin Luther, holding to Jewish and other ancient precedent, excluded the deuterocanonical books from the Old Testament of his translation of the Bible, placing them in a section he labeled "Apocrypha" ("hidden"). To counter Luther's "heresy", the fourth session of the Catholic Council of Trent in 1546 confirmed that the deuterocanonical books were equally authoritative as the protocanonical in the Canon of Trent in the year Luther died. Following Jerome's Veritas Hebraica (truth of the Hebrew) principle, the Protestant Old Testament consists of the same books as the Hebrew Bible, but the order and division of the books are different. Protestants number the Old Testament books at 39, while the Hebrew Bible numbers the same books as 24. The Hebrew Bible counts Samuel, Kings, and Chronicles as one book each, and the 12 minor prophets are one book, and also Ezra and Nehemiah form a single book.

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