This study investigated two phonological processes: assimilation and deletion across three dialects of Yoruba, namely: Ekiti, Ondo and Yagba dialects. The dialects were selected from three major dialects groups of the language: Ekiti from Central Yoruba Group, Ondo from South East Yoruba Group and Yagba from North East Yoruba Group. The study described and compared the operations of the two phonological processes in focus in these three dialects, highlighting similarities and differences. Five language helpers were selected to supply data for each of the dialects, making a total of fifteen language helpers. The language helpers were old people between the ages of seventy (70) years and eighty (80) years. The researcher selected old people because they speak their various dialects more fluently than the younger ones. The younger ones invariably mix the regional dialects with the standard dialects and English language in their linguistic repertoire. The research work made use of Generative Theory (Generative Phonology) and Autosegmental Theory (Autosegmental Phonology). These theories account for the intuitive knowledge of a native speaker about his/her language. While Generative Phonology adequately accounts for segmental units through the postulation of rules, Autosegmental Phonology account for suprasegmental features through postulation of different tiers that are linked by Association lines. Data were presented, analyzed and accounted for at every step of the presentation. The study revealed that the two processes are operative in the three dialects; it further shows that while the dialect show similarities, they also show differences. The study confirms the claim of scholars that dialects reflect different grammatical structure of the same language.

Phonological Processes, Dialects, Assimilation, Deletion, Yoruba language.