Christianity in the Arab world traces its history back to the first century. Prior to the Muslim Arab conquest in the 7th century, much of the Middle East was part of the Christian Byzantine Empire. Even after the advent of Islam, some Christian populations did not become Muslim converts, thus by remaining Christians they maintained their religious identity through to the present day. Some Christian sects that were persecuted as heretical under the Byzantine rule enjoyed greater freedom under their Muslim rulers. Whether the Christians in the Middle East are considered Arab depends on what aspects of the word Arab one wishes to emphasize (political, linguistic, ethnic). (See Arab). For example, some Lebanese Maronites go so far as to emphasize Lebanon's link to the ancient Phoenicians and to limit the label Arab to people living in Saudi Arabia and the Gulf states.

Like Arab Muslims, Arab Christians and Arab Jews for that matter, refer to God as Allah. The use of the term Allah in Arab Christian churches predates its use in Islam by several centuries. In more recent times (especially since the mid 1800's), Arabs from the Levant region have been converted from these churches to Protestant ones, most notably Baptist and Methodist churches. This is mostly due to an influx of Western, predominantly American, missionaries.

Large numbers of Arab Christians can be found in Egypt, Syria, Iraq, Lebanon, Israel and especially the United States. The largest population is found in Egypt, numbering several million. Lebanon contains the highest proportion; it is believed to be about 39% Christian (mainly Maronite, with sizable numbers of Greek Orthodox, Syrian Catholic and other churches). In Syria, Christians form just under 15% of the population. About 6% of all Palestinians are Christian. Some of the Palestinian Christians were converted by American or European missionaries during the colonial period. (see Palestinian Christians). There are significant Christian populations in Iraq (including Assyrian and Chaldean Christians) and Syria (see Jacobite Orthodox Church). Another major group of Arab Christians are the Copts, including some six million Arab-speaking people in Egypt and hundreds of thousands more abroad. This church has historically been seen by Eastern Orthodox and Roman Catholic churches as heretical, although in recent years there have been considerable strides to reconciliation with the Eastern Orthodox communion. There are tiny communities of Roman Catholics in Tunisia, Algeria and Morocco. Most of the members in North Africa however, are foreign missionaries or workers or converted Arabs.

Arab Christians have made great contributions in the Arab-Islamic civilization. Among them were many doctors, musicians, scientists, as well as educators and poets contributors to litrature.

References

http://www.cia.gov/cia/publications/factbook/geos/le.html