reduced, regardless of stress. However, according to Edgar Polomé, these five phonemes can vary in pronunciation. Polomé claims that , , , and are pronounced as such only in stressed syllables. In unstressed syllables, as well as before a prenasalized consonant, they are pronounced as , , , and . E is also commonly pronounced as mid-position after w. Polomé claims that is pronounced as such only after w and is pronounced as in other situations, especially after (y). A can be pronounced as in word-final position. Swahili vowels can be long; these are written as two vowels (example: , meaning "sheep"). This is due to a historical process in which the L became deleted between the second last and last vowel of a word (e.g. "sheep" was originally pronounced kondolo, which survives in certain dialects). However, these long vowels are not considered to be phonemic. A similar process exists in Zulu. Consonants Some dialects of Swahili may also have the aspirated phonemes though they are unmarked in Swahili's orthography. Multiple studies favour classifying prenasalization as consonant clusters, not as separate phonemes. Historically, nasalization has been lost before voiceless consonants, and subsequently the voiced consonants have devoiced, though they are still written mb, nd etc. The /r/ phoneme is realised as either a short trill or more commonly as a single tap by most speakers. exists in free variation with h, and is only distinguished by some speakers. In some Arabic loans (nouns, verbs, adjectives), emphasis or intensity is expressed by reproducing the original emphatic consonants and the uvular , or lengthening a vowel, where aspiration would be used in inherited Bantu words. Orthography Swahili is now written in the Latin alphabet. There are a few digraphs for native sounds, ch, sh, ng and ny; q and x are not used, c is not used apart from the digraph ch, unassimilated English loans and, occasionally, as a substitute for k in advertisements. There are also several digraphs for Arabic sounds, which many speakers outside of ethnic Swahili areas have trouble differentiating. The language used to be written in the Ajami script, which is an Arabic script. Unlike other adaptations of the Arabic script for other languages, relatively little accommodation was made for Swahili. There were also differences in orthographic conventions between cities and authors and over the centuries, some quite precise but others different enough to cause difficulties with intelligibility.