[1] Ajami is a name commonly given to alphabets derived from Arabic script for the use of various African languages, from Swahili to Hausa, Fula, and Wolof.
The first systematic attempt was done by Mwalimu Sikujua, a scholar and poet from Mombasa, who built upon the centuries of Arabic script use in the region.
However, the spread of a standardized indigenous variation of Arabic script for Swahili was hampered by the colonial takeover of East Africa by the United Kingdom and Germany.
Colonial administrators as well as prominent Swahili scholars, despite recognizing the need for implementation of reform in the script, citing local opposition and conservativity, were anxious to do so and impose it on the populace in a top-down manner.
Whereas, Mu’allim Sheikh Yahya Ali Omar from Mombasa decided to do what is done in the Latin script, namely to just write the letters mīm (م) or nūn (ن) as part of the word.
[1] In the most recent and most widely acknowledged orthographic standard, devised by Mu’allim Sheikh Yahya Ali Omar, the dialect of his hometown Mombasa has been chosen as the basis.
[4] Although the Roman orthography does not distinguish between syllabicity and prenasalized sounds, both Sheikh Yahya's manuscripts and Yahya Omar's convention make a distinction between a syllabic nasal followed by a voiced plosive (e.g. [m̩ɓ]) and a prenasalised voiced plosive (e.g. [ᵐb]).
[4][2] Aspirated as opposed to non-aspirated consonants are also marked in Swahili Ajami, with a "two-eyed" hāʾ (ھ) similar to what has been done in the Urdu alphabet.
Dental versus alveolar [t] and [d] are not distinguished in Swahili Roman orthography, nor in unmodified Arabic script.
[4][2] In Swahili Ajami, vowels in the middle of the word are shown differently depending on whether the syllable is stressed on unstressed.
The exceptions to this rule are extremely rare, and are usually found in words borrowed from other languages, mostly Arabic (for example, maalum).
This practice of indicating the stressed syllable also helps to delimit individual words in the Ajami script.
In Swahili Ajami script, to denote vowel sequences, hamza and either alifu (ا), yee (ي), or waw (و) are used.