Roman Catholic and Orthodox Christians (Eastern Orthodox, Russian Orthodox, Ethiopian Orthodox, etc.) have some additional books in their Old Testaments that Protestants do not consider Scripture … . Protestants refer to these books as the Apocrypha, though Roman Catholics call them the deuterocanonical books (literally, the “secondly canonical” books, because they were formally recognized as canonical at a later time—as opposed to the protocanonical, or “firstly canonical,” books). These books were written by Jews in the roughly five-hundred-year period between the Old and New Testaments (430 B.C.—A.D. 40).

Protestants do not consider the Apocrypha as Scripture for a number of reasons. 

1. The Jews who authored the books never accepted them into their canon. This is a weighty argument in that those who wrote and preserved these books put them in a different category from the recognized Hebrew Scriptures. Indeed, comments within the Apocrypha distinguish contemporary writers from the divinely inspired prophets, who had long been silent (1 Macc. 4:41—46; 9:27; 14:40).
2. The Apocrypha contains clear factual errors and, from the standpoint of Protestants, theological errors (such a praying for the dead, see 2 Macc. 12:43-45).
3. The Roman Catholic Church did not officially recognize the books in the Apocrypha as canonical until the Council of Trent in 1546. In fact, Jerome (A.D. 340-420), the translator of the Vulgate (the official Roman Catholic Latin Bible for more than a millennium), claimed the books of the Apocrypha were edifying for Christians but were “not for the establishing of the authority of the doctrines of the church. At the Council of Trent, Roman Catholics recognized the deuterocanonical books in reaction to Protestant leaders who called for a return to biblical Christianity, stripped of later accretions and distortions. Roman Catholics include the Apocryphal books within their Old Testament canon, sometimes adding whole books and sometimes combining apocryphal portions with books Protestants recognize as canonical (for example, three additions to Daniel—The Prayer of Azariah, Susanna, and Bel and the Dragon). These additions and combinations result in a forty-six-book Old t=Testament canon for Roman Catholics.
4. While there are some debatable allusions to the Apocrypha in the New Testament, New Testament authors nowhere cite the Apocrypha as Scripture (that is, with a formula such as “The Scripture says”). Almost every book in the Old Testament is cited as Scripture.