In the 20th century English became the lingua franca of the whole world. The reasons for this process are numerous, and in part complex. In certain areas the impact of English is due to direct contact or friction with a non-English-speaking population (e.g. Aitchison, 1991: Chapter 8; Janson, 2002: Chapter 12). This is especially so in countries under the British Crown in the 19th and early 20th century. The influence of English on other languages (and their speakers) may be more indirect: the penetration of notions, products and terms from an English-speaking country or community to countries whose population do not speak this language. Another way of linguistic influence is the penetration of English vocabulary into a third language through a mediating language, whose speakers have direct contact with English speakers. Such phenomena occur in any interlingual contacts and are not unique to English or Arabic.

The discussion of the effect of English on Arabic should be divided into two parts in accordance with the dual structure of this language, namely written or so-called 'Literary' or 'Standard' Modern Arabic, and colloquial Arabic, which is used for normal oral communication. Modern Literary Arabic is based on rich layers of Classical literature and innovations added down the ages, especially since its renaissance at the beginning of the 19th century. Colloquial Arabic is well known among world languages for its numerous dialects, which vary due to many geographic and demographic factors. This dichotomy between the Literary and Colloquial varieties, called diglossia (see the classic paper by Ferguson, 1959), exists in other languages, but the degree of difference between the two is probably unique to Arabic. A major linguistic problem is the absence of a clear boundary between Literary and Colloquial Arabic, and native Arabic speakers mix numerous features of these varieties in diverse combinations.