Progressive and Regressive Assimilation in Portuguese

The consonants sc usually represent two sounds in Portuguese. In words such as escola (school), fresco (fresh) and máscara (mask), most Brazilians use an alveolar fricative and velar plosive. In standard European Portuguese, however, speakers use an alveopalatal fricative and velar plosive. 

In words such as excelente (excellent), nascimento (birth), and piscina (swimming pool), Brazilian Portuguese speakers use an alveolar fricative, and European Portuguese speakers use an alveopalatal fricative. Though the word excelente has an x, it is not pronounced [ks] but [s]. The reason speakers use one sound in these words is the result of ease of articulation.

The change from two sounds to one sound can be termed consonant cluster simplification. Less articulatory effort is required to articulate one fricative rather than two. Though Brazilian Portuguese has dialects that pronounce the orthograpic s as an alveopalatal fricative before consonants, i.e., escola (school), in words such as piscina (swimming pool), all varieties of Brazilian Portuguese use the alveolar fricative.

In European Portuguese, words such as piscina were once pronounced with the combination of an alveopalatal fricative and alveolar fricative. However, the fricatives became two alveopalatal fricatives. The sound change was a progressive assimilation process. The two alveopalatal fricatives later become one fricative by a degemination process.

However, in Brazilian Portuguese, words such as piscina were once pronounced with the combination of two alveolar fricatives. The sound change which reduced the two fricatives to only one was a degemination process. However, in varieties of Portuguese such as the one spoken in Rio de Janeiro, the two fricatives were once pronounced with the combination of an alveopalatal fricative and alveolar fricative. Unlike in European Portuguese, the sound change which produced one alveolar fricative was not a progessive assimilation process. In contrast, it was a regressive assimilation process. It produced two alveolar fricatives which were later reduced to one by a degemination process.

In words such as excelente, nascimento and piscina, Brazilian speakers use an alveolar fricative, but most European speakers use an alveopalatal fricative. The words used to have two fricatives, but now they have only one. The process which changed the two sounds to one was an assimilation process, but it was different in the two dialects. In European Portuguese it was a progressive assimilation process, but in Brazilian Portuguese it was a regressive assimilation process.