As a member of the dialect continuum of Romance languages, Catalan displays linguistic features similar to those of its closest neighbors (Occitan, Aragonese). The following features represent in some cases unique changes in the evolution of Catalan from Vulgar Latin; other features are common in other Romance-speaking areas.
Phonology
Catalan is one of the Western Romance languages; it is most closely related to Occitan and only diverged from it between the eleventh and fourteenth centuries after the cultural ties with France were broken. In time, Catalan became more tied to the Ibero-Romance languages in Spain; because these languages are significantly more conservative than French (which has been the most important influence over Occitan in the last several hundred years), most of the differences between Catalan and Occitan are due to developments in Occitan that did not occur in Catalan.
Common features with Western Romance languages, but not Italo-Romance
Voicing (and lenition) of intervocalic --, --, -- into -b-, -d-, -g- ( 'goat' > cabra, 'chain' > cadena, 'safe' > segur). Loss of gemination in stop consonants. Development of (later ) instead of from palatalized . For example, ('sky, heaven') > Old Catalan cel > modern (cf. Italian cielo ). Development of in , into palatal (vs. , in Italian). Apicoalveolar pronunciation of and . (This was once common to all Western Romance languages, but has since disappeared from French, some Occitan dialects, and Portuguese.)
Common features with Gallo-Romance languages
Innovations: Loss of final unstressed vowels except - ( 'wall' > *muro > mur, 'flower' >flor); cf. the maintenance of all final vowels except - after in Spanish and Portuguese, e.g. muro but flor; Italo-Romance maintains all final vowels (Italian muro, fiore). The resulting final voiced obstruents undergo devoicing: ('cold') > fred or . However, final voiceless fricatives are voiced before vowels and voiced consonants (regressive voicing assimilation): els homes 'the men' + > ; peix bo 'good fish' + > . (The same final-obstruent devoicing occurs in all of the Western Romance languages to the extent that obstruents become final, but this is fairly rare in Ibero-Romance. Cf. Portuguese luz "light" vs. luzes "lights" , , Old Spanish relox "(wrist) watch" vs. relojes "(wrist) watches" .) (Apparent maintenance of -o in first-person singular and -os plurals are likely secondary developments: Old Catalan had no first-person singular -o, and -os plurals occur where they are etymologically unjustified, e.g. peixos "fishes" < , cf. Portuguese peixes.) Diphthongization of and before palatal consonants (with subsequent loss of middle vowel if a triphthong is produced). Spanish and Portuguese instead raise the vowel to become mid-high; in Spanish, this prevents diphthongization. (But diphthongization between palatals does occur in Aragonese.) Latin 'thigh' > * > cuixa (cf. French cuisse but Portuguese coxa). Latin 'eight' > > vuit (cf. French huit but Portuguese oito, Spanish ocho; Old Occitan both ueit and och). Latin 'bed' > > llit (cf. French lit but Portuguese leito, Spanish lecho; Old Occitan both lieig and leit). Conserved features: Preservation of initial -, -, - ( 'fold' > aplegar 'to reach', 'key' > clau, 'flame' > flama); cf. palatalization of these initial clusters in Spanish llegar, llave, llama Portuguese chegar, chave, chama. In the Italo-Romance group this slenderization generally replaces the second consonant with -i- (vocalization); hence Italian piegare, chiave, fiamma.
Common features with Occitan, French, and Portuguese, but not Spanish
Initial + yod or or , + yod, > > or (in contrast to Spanish before stressed non-back vowels)
Conserved features: Preservation before unstressed non-back vowels of the consonant that developed from initial + yod or or , + yod, , in contrast to its loss in this context in Spanish: ('freeze') > gelar (cf. Spanish helar ; but Portuguese, Occitan gelar). ('lay down') > *gieitar > gitar (cf. Spanish echar; but Portuguese jeitar, Occitan gitar, French jeter).