(orthography) The vowel diacritics in Hebrew and Arabic, which are not normally written, but which are used in dictionaries, children's books, religious texts and textbooks for learners.
(phonology) The change in pronunciation of historically or variably consonant (typically sonorant) sounds as vowels. For example, the syllabic /l/ in words like people or the coda one in words like cold or coal are variably realized as a high back vowel or glide—[ʊ], [u], [ɤ] or [o]—in many dialects of English in the US, UK, and the Southern Hemisphere. For example, in African American Vernacular English, one common pronunciation of the words "people", "cold", and "coal" is [pʰipʊ], [kʰoɤd], or [kʰoɤ] respectively.
