Protocanonical books
The protocanonical books are those books of the Old Testament that are also included in the Hebrew Bible and that came to be considered canonical during the formational period of Christianity. The term protocanonical is often used to contrast these books to the deuterocanonical books or apocrypha, which "were sometimes doubted" in the early church, and are considered non-canonical by most Protestants.
List
The list of protocanonical books is Genesis, Exodus, Leviticus, Numbers, Deuteronomy, Joshua, Judges, Ruth, 1–2 Samuel, 1–2 Kings, 1–2 Chronicles, Ezra, Nehemiah, Esther, Job, Psalms, Proverbs, Ecclesiastes, Song of Solomon, Isaiah, Jeremiah, Lamentations, Ezekiel, Daniel, Hosea, Joel, Amos, Obadiah, Jonah, Micah, Nahum, Habakkuk, Zephaniah, Haggai, Zechariah, and Malachi.
Enumeration
These books are typically 39 in number in most English-language bibles. Based on the Jewish tradition of the Tanakh, these same books may be counted as 24 books, counting the twelve minor prophets together as one book, one book each for 1 and 2 Samuel, 1 and 2 Kings, and 1 and 2 Chronicles, as well as a single book for Ezra and Nehemiah. In his prologues, Jerome counted the same content as 22 books, combining Jeremiah with Lamentations and Judges with Ruth. The list given in Codex Hierosolymitanus numbers the same books at 27.