The name Ajami comes from the Arabic word for 'foreigner'. It is the name given collectively to modified versions of the Arabic script used to write various West African (non-Arabic) languages. With the spread of Islam and Islamic culture to the African continent, speakers of some African languages, such as Kiswahili, Hausa, Wolof, Mandinka and Fulfulde, wanted to write their languages in the script.

Fulfulde Ajami. Copied with permission from Souag, L. (2011). 'Ajami in West Africa'. Afrikanistik online, Vol. 2010. Original source: Sow, Alfâ Ibrâhîm (ed.) (1971) ' Le Filon du bonheur éternel, par Tierno Mouhammadou-Samba Mombéyâ'

The oldest known Ajami manuscripts date from the 14th century and were found in Mali. The script became widespread across the Sudanic belt, and was adapted for secular uses. Traders would record business transactions in Ajami, while other people would write secular poems or compile medical encyclopedias of indigenous treatments. It was used to write about a dozen languages. In some parts of Africa in the 20th century, Ajami was the medium of the anticolonialist resistance movement, as, in order to read it, knowledge of both the Arabic script and the language being written is required, and the colonialists did not typically have access to this knowledge. In Nigeria, Hausa is the only native language represented on currency; Nigerian bank notes have their values written in Hausa, using Ajami.

Efforts on the part of the Islamic Education, Scientific and Cultural Organization (ISESCO) to standardize Ajami have not been successful. Usage varies significantly between and even within languages, from one author to another. Two of the most widely documented languages which use Ajami are Wolof and Hausa.

The Wolof language has officially been written in the Latin script since the 1970s, although some scholars claim that the population literate in Ajami (called Wolofal for this language) is greater than that literate in Latin, due to higher attendance in Quranic than secular schools. Nine of the twenty-eight Arabic letters are not used for writing Wolof, except in Arabic loan words. There are fourteen sounds in Wolof which are not found in Arabic, mostly prenasals. Generally, these are written using the Arabic letter which is deemed to represent the closest sound to the target (this is subject to dialectal variation), modified with the three dot symbol above or, less often, below. Some letters are used to represent more than one sound; the rules governing this are inconsistent. Arabic writing typically indicates short consonants and long vowels, of which there are three. These vowels are represented using the letters ya [i], waw [u] and aleph [a]. The Wolof language uses seven vowels. These are written using the same three letters; ya to write front vowels [i, e, ɛ], waw to write back vowels [ɔ, o] and aleph to write mid-vowels [a, ə]. Diphthongs are written using a combination of a vowel and a semi-vowel having a sukun (small circular diacritic), in both Arabic and Ajami writing. Long consonants and short vowels are optionally indicated in both scripts using diacritics.

Islamic catechism in the Wolof language. From Cheikhouna Lo N’gabou, 2003.

The Hausa language shares a syllabic inventory with Arabic; CV, CVV and CVC. The sound systems of both languages also overlap significantly, which facilitates the use of the Arabic script for writing the language. There is no standard for writing Hausa in Ajami, so there is a great deal of variation. However, some orthographic conventions are generally adhered to. Hausa uses five vowels, [a, e i, o u], whereas Arabic only uses three, [a, i, u]. Each letter has a long and a short counterpart in both languages. The letters which are used in both languages are written in Hausa Ajami according to the rules of the Arabic script. To represent the extra two vowels, Hausa Ajami uses the Arabic waw for both [o] and [u]. The reader must deduce which representation is intended from the context. To write a short [e] vowel, Hausa Ajami uses a dot diacritic below the consonant, and to write a long [e], it uses a dot diacritic below and a vertical stroke above. Hausa is a tone language, but this is not reflected in Ajami writing. There are five sounds in Hausa which are written with modifications of Arabic letters: [ɓ], which modifies the Arabic [b] sign; [c], which modifies the Arabic [t] sign; [ɗ], which modifies the Arabic [tc] sign; [g], which modifies the Arabic [ʔ] sign; and [tʃ], which modifies the Arabic [z] sign.