Catalan, a pluricentric language, presents a wide range of dialectal variation in its phonology.
The differences in the vocalic systems is the main criteria used to differentiate between the major dialects: Wheeler distinguishes two major dialect groups, western and eastern dialects. Eastern Catalan includes Northern Catalan, Central Catalan, Balearic, and Alguerese. Western dialects include Valencian and North-Western Catalan.
Regarding consonants, betacism, fortition, certain elisions, and fricative–affricate alternations are the most prominent differences between dialects.
Vowels
Close vowels /i/ and /u/
The degree of vowel openness is greater than in Spanish realizations and is similar across Central Catalan, Mallorcan, and Valencian. It appears that, consistent with the relatively open realization of mid vowels, the high vowels in Valencian, Mallorcan, and Menorcan are also slightly more open than in the rest of the linguistic domain. A comparison of data regarding vertical and horizontal lip opening for a speaker from Lleida and a Central Catalan speaker suggests that is somewhat more closed in the Lleida dialect. Meanwhile, in Northern Catalan is more open than in General Catalan. This observation aligns with the possibility that, given the reduced number of vowel phonemes in Northern Catalan, all vowels in this dialect are more "relaxed" and "imprecise" than their counterparts in other dialects.
In general, the high back vowel is more open in Catalan than in Spanish, and it exhibits a similar degree of openness in Central Catalan, Mallorcan, and Valencian. It appears that, consistent with the relatively open realization of mid vowels, high vowels are slightly more open in Valencian, Mallorcan, and Menorcan than in the rest of the linguistic domain. The realization of is somewhat closer in the Lleida dialect than in Central Catalan; on the other hand, the vowel is likely more open and centralized in Northern Catalan than in Central Catalan.
Close-mid vowels /e/ and /o/
The realization of in Central Catalan exhibits less oral opening than the corresponding in Spanish. There are differences in vowel openness across the Catalan linguistic domain. On one hand, it has been observed that is higher in North-Western Catalan than in Central Catalan. Subsequently, it has been reported a smaller gap between the incisors and a greater horizontal separation of the lips during the production of in the Lleida dialect compared to Central Catalan; consistent with these observations, a very noticeable closing of the vowel has been noted in the Pallars dialect. On the other hand, appears less low in Central Catalan than in Mallorcan, Valencian, and Alguerese; it is possible that it is also particularly centralized and retracted in Alguerese. Linguistic Atlas of the Iberian Peninsula (ALPI) transcriptions support the existence of a more open in Valencian and Balearic than in Central and Northwestern Catalan, but they do not confirm the existence of a less open in North-Western Catalan compared to Central Catalan. Transcriptions from Diccionari català–valencià–balear (DCVB) indicate a particularly open quality of unstressed in El Comtat, La Safor, La Marina, and Baix Vinalopó. These differences in quality also apply in unstressed positions.
The realization of in Central Catalan exhibits less oral openness than the corresponding in Spanish. Similarly to the case of , the of North-Western Catalan (Lleida dialect) appears closer than that of Central Catalan, although the ALPI does not record this difference. In turn, Mallorcan, Menorcan, and Valencian varieties show more open realizations of the vowel than Central and Northwestern Catalan. Added to these differences is the particularly close quality of the vowel in those transitional areas between the dialects of Catalonia and Roussillon that still maintain the opposition between and .
Mid central vowel /ə/
The central mid vowel (both stressed and unstressed) is slightly closer and more rounded in Mallorcan than in Central Catalan. An intensification of this articulatory characteristic can perhaps be observed in the rounded realization of the stressed variant in towns such as Capdepera, Artà, and Son Servera, regardless of the context.
Open-mid vowels /ɛ/ and /ɔ/
Open-mid front unrounded vowel /ɛ/
There are three variants of within the Catalan linguistic domain, based on the degree of oral aperture.
One variant is found in Central Catalan and the Lleida dialect, with a degree of openness greater than that of the most open variant of in Spanish; the realization in the Lleida dialect is slightly closer than the realization in Barcelona.
A second variant is closer than the previous one, found in Pallars and Alguerese.
A third variant is more open than in Central Catalan, and is found in the southern zones of North-Western Catalan, in Valencian—especially south of Camp de Llíria and l'Horta—and in Balearic Catalan (at least in the Mallorcan and Menorcan varieties). Data from the ALPI indicate that the Valencian realization tends to be slightly more open than that of the Ibizan (Eivissan), Menorcan, and Mallorcan varieties (the latter in the majority of towns). In some regions (Lower Aragon; La Canyada de Biar; Ports), the particularly open nature of the stressed has fostered a phenomenon of bimatization—resulting in , , or —especially before opening consonants (implosive and ) and in vernacular words. A subsequent process of dissimilation between the two resulting elements generates the diphthongs , , and (e.g., viard, pial for , ); indeed, in specific cases, the bimatized solution remains the exclusive form or alternates with [jV]-type diphthongs. The diphthongized realization has extended to unstressed positions in some areas (Lower Aragon, La Canyada de Biar).
Open-mid back rounded vowel /ɔ/
There are three variants of based on the degree of oral aperture.
A variant more open than the open variant of in Spanish, found in Central Catalan and Lleida Catalan.
A variant more closed than the previous one, found in North-Western Catalan and Algherese.
Another variant is more open than the Central Catalan one, and is found in Valencian and Balearic (especially in Mallorcan and Menorcan, more so than in Ibizan (Eivissan)). The very open realization of in Valencian and Balearic fosters other realizations: , (frequent in Artà, Campos, Son Servera, Felanitx, Llucmajor, Sineu, and the Valls del Vinalopó); and cases of diphthongization ( in La Sorollera). In Felanitx, the particularly open realization of may have been favored by the fact that is produced there with a particularly palatal realization; this explanation could also apply to the pronunciation of in other localities (Son Servera, Sineu, Campos). Also noteworthy is the particularly closed quality of the vowel in the transition zone between the northern dialects of Catalonia and Northern Catalan areas that still maintain the opposition between and .
Open vowel /a/
There are four variants of across the linguistic domain:
One variant in found in Central Catalan, Lleida Catalan, and Algherese, which is more open and back (somewhat close to ) than the General Spanish .
A variant that is closer and more fronted ( or ) than the first variant, is found in Valencian and in North-Western Catalan—both the western sub-dialect (Ribagorçan); the lower Aragon border, and the southern sub-dialect.
A variant that is even closer and more fronted than or , depending on the locality, particularly in Mallorcan and Menorcan; conversely, the Ibizan (Eivissan) pronunciation appears to align more closely with the first variant of Central Catalan. Consistent with these articulatory descriptions, the spectrum of in Mallorcan shows a lower F1 than that of the found in Central Catalan.
A variant that is less open and more centralized than the of General Catalan, found in Northern Catalan in Roussillon. This realization is produced with less vertical and horizontal lip separation than the realization found in the other dialects.
The particularly close and fronted nature of the stressed has fostered instances of bimatization or diphthongization in certain areas: and in Son Servera; following a palatal consonant in Son Servera; and occasionally , , and in fronting contexts in Lower Aragon. Conversely, various sociolinguistic factors have recently led to realizations of that are less fronted in certain Mallorcan centers—such as Son Servera, Felanitx, and perhaps even Palma—suggesting a possible ongoing process of change.
Consonants Sonorants
Nasals /m/, /n/, /ɲ/, /ŋ/
presents different pronunciations depending on its position.
before plosive: in Mallorcan, Menorcan, and Alguerese exhibits regressive assimilation of place of articulation—a process that is also quite systematic in colloquial Valencian—whereas in transitional Northern–Central Catalan, does not appear to be regressive assimilation of place when the consonant cluster involves a nasal.
before nasal: the cluster can become through a process of regressive assimilation in the southern part of the Valencian Community (e.g., 'column') and in southern Northwestern Catalan (e.g., co no for 'of course'; Lower Aragon). The geminate cluster /mm/—when not occurring in a prefixed word—is often simplified in colloquial speech ( instead of in words like 'gem' or 'height', 'peak'), likely due to the influence of Spanish. In Northern Catalan, by contrast, French words spelled with have been adopted with (e.g., Fr. ).
before fricative and approximant: in Mallorcan, Menorcan, and Alguerese generally exhibits regressive assimilation of place; such assimilations are also quite common in colloquial Valencian. Consequently, the word-final cluster -ms becomes -ns. In colloquial speech, the medial intervocalic cluster /ms/ can become through regressive assimilation in many areas of the linguistic domain (e.g., *prensa instead of 'press').
before rhotics: in word-internal position, pronunciations such as *sonriure (alongside 'smile'; cf. Lower Aragon) have arisen through assimilation and/or Spanish influence.
before lateral: regressive assimilation of to occurs in various dialects in colloquial speech (Lower Aragon). Assimilations of manner are less systematic: in Mallorcan, regressive assimilation of to may occur, while in Alguerese, progressive assimilation of to takes place.
in postconsonantal position: the consonant retains its bilabial realization following any consonant. In the Alicante dialect, the word-final cluster -rm may simplify to -r due to the articulatory weakening of the second consonant (C2) in this context.
presents different pronunciations depending on its position.
before plosive: the process of regressive assimilation in optional cases is possibly more frequent than when C1 is an oral dental plosive.
before nasal: before , the palatalization of is obligatory throughout the entire linguistic domain, except, perhaps, in those territories where the high degree of palatal quality in results in being the only possible realization. Optional assimilations are more frequent here than in the case of clusters consisting of an oral stop followed by a nasal stop; for instance, the contact between a prefix-final /n/ and a root-initial is invariably resolved as (e.g., 'immortal', 'commiseration'), although pronunciations have been recorded in areas bordering the Aragonese-speaking region (e.g., *inmemorial 'immemorial' in Lower Aragon, *inmens 'huge' in Lower Cinca). The geminate cluster that does not arise from prefixation (e.g., 'innovate', 'connatural') is often simplified in colloquial speech ( instead of in words like 'biennial', 'mindset', 'Anne'), likely due to the influence of Spanish.