The occurrence of schwa epenthesis is governed morphophonemically. Additionally, arises during epenthesis or vowel reduction. This differs from orthographic conventions of the early 20th century that did reflect this epenthesis. This mechanism can be described as a form of anaptyxis (vocalic epenthesis). A complex example of epenthesis is , from + . Some phonological processes do occur, however, including assimilation, epenthesis, lenition and reduplication. Vowels that are inserted via epenthesis sometimes depend upon the adjacent consonants. Non-homorganic clusters are separated by vowel epenthesis even across word boundaries. Regular or semi-regular epenthesis commonly occurs in languages with affixes. A metathesis and a word-initial epenthesis produce "E-trus-ci". A consonant may be added between vowels (epenthesis) to prevent hiatus. The phonological/morphophonological processes observed include syllabic reduction, epenthesis, deletion, and reduplication. However, Zamenhof stated that in "severely regular" speech such epenthesis would not occur. Initial and final consonant clusters are not tolerated, and schwa epenthesis is pervasive. Epenthesis arises for a variety of reasons.