The deuterocanonical books are the books that Catholicism, Eastern Orthodoxy, and Oriental Orthodoxy include in the Old Testament that were not part of the Jewish Tanakh. Their acceptance among at least some early Christians is generally well-testified, and as early as the Council of Rome in 382, an official canon including these books was published.
In the Catholic Church, the following books are considered deuterocanonical: Tobit, Judith, 1 Maccabees, 2 Maccabees, Wisdom of Solomon, Sirach (Ecclesiasticus), and Baruch; as well as some additions to Esther and Daniel. The various Orthodox churches include a few others, often including 3 Maccabees, Psalm 151, 1 Esdras, Odes, Psalms of Solomon, and occasionally even 4 Maccabees. This last book is often relegated to an appendix, because it has certain tendencies approaching pagan thought.
There is also a strong tradition of studying the Book of Enoch in the Ethiopian church, a denominational family in the Oriental Orthodoxy.
Like Jews, most Protestants exclude these books as apocryphal. The word 'deuterocanonical' comes from the Greek for 'second canon'. In Catholicism, this term means that the canonicity of the books was definitively settled at a later date than the rest of the canon. Among Orthodox, the term usually indicates that they were composed later than the Hebrew Bible.
Most Septuagint manuscripts include the deuterocanonical books and passages. Like the New Testament, the deuterocanonical books were mostly written in Greek. Several appear to have been written originally in Hebrew, but the original text has long been lost. Archeological finds in the last century, however, have provided a text of almost 2/3 of the book of Sirach, and fragments of other books have been found as well. One of these books, 2 Esdras, survives only in an ancient Latin translation dated to the second century AD but was probably composed in Greek. This particular book is not widely accepted by the Orthodox and is rejected by Catholics.
Using the word "apocrypha" implies that the writings in question should not be included in the Bible, lumping them together with certain apocryphal gospels and other New Testament Apocrypha. The Style Manual for the Society of Biblical Literature recommends the use of the term "deuterocanonical literature" instead of "Apocrypha" in academic writing.
- Canon of the Old Testament (http://www.newadvent.org/cathen/03267a.htm) at the Catholic Encyclopedia (http://www.newadvent.org/cathen/)
- Deuterocanon Use in New Testament (http://scripturecatholic.com/deuterocanon.html)
- Deuterocanonical books (http://st-takla.org/pub_Deuterocanon/Deuterocanon-Apocrypha_El-Asfar_El-Kanoneya_El-Tanya__0-index.html) - Full text from Saint Takla Haymanot Church Website (also available the full text in Arabic