Phonological rules are necessary to generate the phonetic form from the underlying phonemic form.
Rules involving assimilation include alveolar stop assimilation, liquid and glide devoicing, vowel nasalization, and vowel harmony. Rules of dissimilation include fricative dissimilation. Rules of insertion include voiceless stop insertion and glottal stop insertion. Other phonological rules include vowel lengthening, aspiration , and flapping. Palatalization of consonants is also a common process.