There are a number of contexts where the addition of a suffix causes a change in the quality of the last consonant or vowel of a stem. Certain of these changes are confined to specific lexical items, whereas others occur as part of a general phonological process in the language. There are a number of nouns in which the high vowel of the final syllable in the bare form does not appear when a suffix beginning with a vowel is attached to the root. Many of these are words of Arabic origin which do not have a vowel in this position. It is not possible to know without looking in a dictionary whether the final high vowel in the bare form of a root is epenthetic or not. In the spoken language, some suffixes which conjoin to a stem by means of the consonant 'y' may affect the pronunciation of a preceding 'a', 'e', 'u' or 'u'.