THE ARABIC LANGUAGE
First, Arabic is an Afro Asian language, attested as early as the 7th century. Second, if it covers a large part of the world, it gathers many dialects, more or less different from each other. Depending on the region, that may lead to problems of understanding between Arab people.
Wrongly, many consider it quite harsh to hear, like German. But what is true is that Arabic is a rich and complex language.
In the world
With more than 300 million speakers, Arabic ranks among the top in the world. By far, it is at least the most widely spoken one of the Semitic branch, well ahead of Hebrew and Amharic in Ethiopia.
To varying degrees, people speak it in North Africa, Arab countries of the Middle East, as well as Arab diaspora. This is the result of the expansion of the Arab empire in the Middle Ages. As it reaches 3 continents, both Arabic and non Arabic peoples speak it. It is also the official language of 25 states, which ranks it just after English and French. Thus, in addition to the 22 states of the Arab League, we found it in Eritrea, Chad and West Sahara. A part of Somalia also uses it as main language. That said, the illiteracy rate in the Arab world is still close to 50%.
If Arabic now spreads a lot thanks to Islam, it is not a new fact. Indeed, that happened in the past already. Thanks to trades, in the Middle ages, many countries borrowed Arabic words about flowers, spices, materials. As well as from sciences and technics. That same trend lasted until Renaissance in chemistry, botany and maths fields. Finally, from Napoleon's Egyptian campaign and France's colonial conquests in North Africa in the 19th century, French borrowed from Arabic. Even more today in the daily life, the French use many Arabic words in slang and for Arab fashion or food.
We think the origin of the Arabic language back to the 2nd century. In fact, linguists give it much earlier origins, obviously under much older forms. Thus, the famous Queen of Sheba, the region of ancient Yemen and extinct Arab tribes would have spoken it. By the way, the oldest pre Islamic Arabic written traces date from 267.
Also, the Abd Daghm, people from Taif, are the ones who gave birth to the Arabic writing script.
The role of Islam
If Arabic is much older than Islam, it has grown thanks to the latter. That is so true today. This strong link between a great religion and a language allowed to sacralize Arabic and maintain unity across time and space. This is why the Western world easily associates Islam and Muslims with Arabic. Indeed, they think that Islam and the Arabic speaking world form a whole.
The links between Arabic and Islam are clear and people who convert to Islam often learn Arabic at the same time. Yet some Islamised people did not adopt Arabic. And some Arabised people never became Islamic. Other non Arabic speaking Muslims (Sunni or Shia) live in Turkey, Iran, Pakistan, Bangladesh and Indonesia. In Africa, non Arabic speaking Muslims are in Mali, Niger, Somalia and the Comoros. These people use more than 20 dialects such as Turkish, Farsi or Persian (Iran), Berber (Algeria), Bahasa (Indonesia) and Urdu (Pakistan).
With some limits
Less usual, some Arabised people have not choosen Islam as religion. This is the case in Malta. Although Maltese is similar to Arabic, people has remained Christian. Same thing with the Lebanese who speak Arabic, as well as French, but remain Christian. In Egypt, there are Coptic Christians, too.
Of the 1.25 billion Muslims in the world, only 160 have any real knowledge of standard Arabic. In other words, 90% of Muslims cannot read the Koran in the original text. Thus, the words "Muslims", "Arabs" and "Arabic speakers" have their own meaning.
Please note that Arabic has no 'civil' status in large Muslim countries where Arabic is not official. There, it is a religious language instead.
TO GO DEEPER
It is the result of both 17th century Arabic and the fusion of dialects resulting from conquests and mixing of South Arabian, Berber, African and other dialects. Today, many of them remain and persist throughout the Arab world. It is Arabic that everyone speaks and which conveys a whole culture. However, the latter is often perceived as vulgar and exists only orally.
There are two main groups of Arabic: the Western group and the Eastern group. On the one hand, the Western group includes Arabic spoken in Andalusia (Spain), Maghreb countries (Tunisia, Algeria, Morocco, Libya, Mauritania and West Sahara) and Malta. On another hand, the Eastern group includes Arabic spoken in Egypt, Djibouti, Sudan and Chad. As well as in the Mashreq states and the Arabian Peninsula. To that , we can add some Arabic dialects spoken by some tribes.
Also, not only does each country have its own Arabic, but it can vary between regions and even between cities.
Standard Arabic is taught throughout the world. It has a prestigious aura strongly linked to religion, literature, science, technology and state functions. Despite this, very few Arabs in the world speak it as their mother tongue. Indeed, we count only 120 million speakers who use it as a second language. However, it differs somewhat from the language used to write the Koran 14 centuries ago. This, even if the basic rules have not changed since then.
Of course, it underwent some changes under the "Nahda". This movement is a group of intellectuals from Lebanon, then from Egypt and also from Syria and Palestine. These reformers aimed to modernise the Arabic language. This was done by making the original 7th century syntax somewhat simplier. But above all, by adding modern words. Almost 60% of the modern lexicon comes from this reformed Arabic. It still retains its main eloquent features, which allow skilled speakers to create stylistic forms, hence the term 'eloquent Arabic'.
Islam is never far
Some very pious Arabs see Arabic as the language with the greatest resources and richest lexicon ever. As the sacred language of the Koran, it could not be otherwise, nor be subject to any change. But others see it as mere filler, verbosity or empty display. Perhaps this is why it is almost not possible to write and speak a perfect modern Arabic. As much as dialectal Arabic can be a simple language to use, standard Arabic may seem complex and hard. This explains to some extent why some Arabic speaking people have not took it as their mother tongue. Also, due to its such strong religious aspect, all attempts to reform it failed. And it goes much further, since those who dare to do so are accused of imperial Zionist plot.
Despite tensions, there are very strong links between these two types of Arabic. And this, in history, as well as ideology and language. Indeed, the script, syntax and word order are quasi the same. But words and way to pronunce may vary as Modern Arabic loses all local traces. For this reason, the Arabs have always thought that there is only one Arabic language. Only standard Arabic is written, although dialectal Arabic can theoretically be written.