Like all Romance languages, the Iberian Romance languages descend from Vulgar Latin, the nonstandard (in contrast to Classical Latin) form of the Latin language spoken by soldiers and merchants throughout the Roman Empire. With the expansion of the empire, Vulgar Latin came to be spoken by inhabitants of the various Roman-controlled territories. Latin and its descendants have been spoken in Iberia since the Punic Wars, when the Romans conquered the territory (see Roman conquest of Hispania).
The modern Iberian Romance languages were formed roughly through the following process:
Common traits between Portuguese, Spanish and Catalan
This list points to common traits of these Iberian subsets, especially when compared to the other Romance languages in general. Thus, changes such as Catalan vuit and Portuguese oito vs. Spanish ocho are not shown here, as the change -it- > -ch- is exclusive to Spanish among the Romance languages.
Between Portuguese, Spanish and Catalan
The length difference between r/rr is preserved through phonetic means, so that the second consonant in words such as caro and carro are not the same in any of the three.
Latin U remains [u] and is not changed to [y].
Between Spanish and Catalan, but not Portuguese
The length difference between n/nn is preserved through phonetic means, so that the second consonant in words such as año (Latin anno) and mano are not the same.
The length difference between l/ll is preserved through phonetic means, so that the second consonant in words such as valle and vale are not the same. This also affects some initial L in Catalan.
Between Spanish and Portuguese, but not Catalan
Initial Latin CL/FL/PL are palatalized further than in Italian, and become indistinguishable (to CH in Portuguese and LL in Spanish).
Final e/o remains (although its pronunciation changed in Portuguese, and modern European Portuguese drops final E).
The synthetic preterite, inherited from earlier stages of Latin, remains the main past tense.
Between Portuguese and Catalan, but not Spanish
Velarized L [ɫ], which existed in Latin, is preserved at the end of syllables, and was later generalized to all positions in most dialects of both languages.
Stressed Latin e/o, both open and closed, is preserved so and does not become a diphthong.
Politically (not linguistically), there are four major officially recognised Iberian Romance languages:
Portuguese, official language in eight countries including Portugal and Brazil. After Spanish, Portuguese is the second most widely spoken Romance language in the world with over 250 million speakers, currently ranked seventh by number of native speakers. Various Portuguese dialects exist outside of the European standard spoken in Portugal.
Galician, co-official in Galicia and also spoken in adjacent western parts of Asturias and Castile and León. Closely related to Portuguese, and to an extent Spanish. It shares origins with Portuguese, from the medieval Galician-Portuguese. Modern Galician is spoken by around 3.2 million people and is ranked 160th by number of speakers.
The Iberian Romance languages are a conventional group of Romance languages. Many authors use the term in a geographical sense although they are not necessarily a phylogenetic group (the languages grouped as Iberian Romance may not all directly descend from a common ancestor). Phylogenetically, there is disagreement about what languages should be considered within the Iberian Romance group; for example, some authors consider that East Iberian, also called Occitano-Romance, could be more closely related to languages of northern Italy (or also Franco-Provençal, the langues d'oïl and Rhaeto-Romance). A common conventional geographical grouping is the following:
^Bec, Pierre (1973), Manuel pratique d'occitan moderne, coll. Connaissance des langues, Paris: Picard
^Sumien, Domergue (2006), La standardisation pluricentrique de l'occitan: nouvel enjeu sociolinguistique, développement du lexique et de la morphologie, coll. Publications de l'Association Internationale d'Études Occitanes, Turnhout: Brepols
^Myers-Scotton, Carol (2005). Multiple Voices: An Introduction to Bilingualism. Wiley-Blackwell. p. 57. ISBN978-0-631-21937-8.