Phonetic and phonological variation in Romance dialects: lenition, lexical conditioning, and a frequency-based mapping of /b β v/

• Examines contrast preservation, weakening, and merger in /b β v/ across Romance. • Frequency- and CI-based atlas analysis reveals region-specific phonetic variation. • Variation reflects positional asymmetries, lexical and contact-based effects. • Irregular realisations challenge structural accounts of segmental change. • Clarifies and visualises the geographic distribution of /b β v/ realisations. This study investigates how phonological contrast in Romance may be preserved, weakened, or neutralised under certain conditions, focusing on the phenomenon of betacism , a process whereby /b/ and /v/ (or /β/) tend to merge into a single phoneme. Whereas structural models have tended to treat betacism as a uniform shift, the findings suggest that the erosion of this contrast reflects interacting phonetic, lexical, and sociolinguistic pressures, including lenition, lexical conditioning, and contact-induced change. The analysis focuses on the realisation of /b β v/, showing how phonetic overlap and irregular patterns emerge through positional asymmetries and specific lexical items. The dataset draws on regional linguistic atlases from Romania, Italy, France, Spain, and Portugal. It applies a frequency-based mapping approach by integrating these atlases to document how the /b/-/v/ (or /b/-/β/) contrast varies across dialects and between word-initial and intervocalic contexts. Lexical identity and prosodic position appear to condition outcomes, which may be compatible with usage-based and contact-sensitive models of sound change. These findings also suggest the potential role of lexical irregularity in shaping phonological outcomes. The research provides a comprehensive empirical account of /b β v/ variation and outlines a framework that can serve as a replicable model for examining phonological contrast weakening through combined structural, lexical, and areal perspectives. It offers methodological tools that may inform broader discussions of phonological contrast beyond betacism, particularly through quantitative geolinguistic mapping.