Betacism

In historical linguistics, betacism (UK: /ˈbiːtəsɪzəm/, US: /ˈbeɪ-/) is a sound change in which [b] (the voiced bilabial plosive, as in bane) and [v] (the voiced labiodental fricative [v], as in vane) are confused. The final result of the process can be either /b/ → [v] or /v/ → [b]. Betacism is a fairly common phenomenon; it has taken place in Greek, Hebrew, Japanese, and several Romance languages.