Miae Ahn (2023). “A Study of the /ㅜ/ Replacement of /ㅗ/ in Korean Messenger Corpus”. The Sociolinguistic Journal of Korea, 31(2), 157-176. This study examines the realization of the /ㅜ/ replacement of /ㅗ/ observed at the end of words in the messenger conversation corpus(MCC), comparing it with the results from the “Seoul Corpus(SC; Yoon Y. K. 2020)”. In the "MCC", the frequency of /ㅜ/ replacement of /ㅗ/ was investigated in the following order: postposition, connection ending, and adverbs. Among these, adverbs exhibited the highest realization rate for the /ㅜ/ replacement. In contrast, connection ending and surveys in the SC showed similar frequencies (43.8%, 52.1%). The /ㅜ/ replacement rate for connection ending was found to be 43.8%, while for surveys and adverbs, it was 52.1% and 51.3%, respectively. Furthermore, the analysis revealed that the /ㅜ/ replacement rate of /ㅗ/ was consistently high in all linguistic contexts in the "SC" However, the text-based "MCC" exhibited a lower realization rate for the /ㅜ/ replacement of /ㅗ/ compared with to the natural speech. This discrepancy is attributed to the influence of text-based conversations, which incorporatesphonetic notation consciousness reflecting linguistic norms and the phonetic preferences of the conversation participants. In conclusion, this study provides valuable insights into the realization patterns of the /ㅜ/ replacement in different linguistic contexts, shedding light on the variations between text-based and natural speech corpora.