Betacism

Betacism is a sound change or pronunciation pattern in which /b/ and /v/ merge or interchange. It can make words distinguished by these sounds homophones.

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Voiced bilabial plosive: A consonant sound made by closing both lips and releasing the closure with vocal-fold vibration. This is the articulatory sound /b/ that may merge with /v/.
Vulgar Latin: The nonliterary varieties of Latin spoken across the Roman world, ancestral to the Romance languages. Its regional varieties developed differing outcomes for Latin /b/ and /w/.
Spanish b and v: The Spanish spelling distinction between b and v, whose standard pronunciations represent the same phoneme. It is a familiar case where two letters do not mark a /b/–/v/ contrast.
Rotacism: A sound change in which a sound becomes /r/ or an /r/-like sound. It names a different consonant change, despite the similar term ending.
Voiced labiodental fricative: A consonant sound made by forcing air between the lower lip and upper teeth while the vocal folds vibrate. This is the articulatory sound /v/ that may merge with /b/.
Spanish phonology: The sound system and pronunciation patterns of Spanish. Spanish commonly pronounces written b and v with the same phoneme.
Betacism in Portuguese: The historical merger of Latin /b/ and /w/ in the development of Portuguese and other western Romance varieties. Portuguese illustrates a historical pathway that differs from Spanish's later pronunciation pattern.
Lambdacism: A pronunciation pattern involving substitution, distortion, or loss of the sound /l/. It concerns /l/, not the /b/–/v/ relationship.
Phonemic merger: A sound change that causes two previously distinct phonemes to become one in a language. Betacism can eliminate the contrast between /b/ and /v/.
Latin phonology: The sound system of Latin as reconstructed across its historical stages and varieties. Latin's changing consonant system provides the historical background for Romance betacism.