The formation of Iberian Romance languages followed more or less this process:
- A common Latin/Romance language with dialectal differences extending through all ancient Roman Empire - during this stage, we can speak of the romance language, although, probably, it was quite different from one region to another. It can still be called Popular or Vulgar Latin.
- Separation of Catalan for one side and the rest of Iberian Romance for the other. During this stage a set of romance dialects was spoken in Muslim areas of Iberia called Mozarabic. Catalan is regarded as a transition language between Iberian Romance and Gallo-Romance.
- Iberian Romance splits between Castilian and Galician-Portuguese (among other dialects/languages).
- Galician-Portuguese splits into two languages (although some still consider them the same language): Galician and Portuguese. Portuguese split from Galician when the Portuguese population contacted with speakers of Mozarabic - this explains why Portuguese has so many words of Arab origin (borrowed from Mozarabic).
- Portuguese and Galician: The fact that a Portuguese kingdom was formed allowed the formation of a distinct Portuguese language, based on the ancient Galician-Portuguese romance. Early Portuguese can be seen as codified Galician-Portuguese. Separation and eventual codification of Galician led to these two varieties being considered different languages today.
- Spanish: The Castilian Crown pushed for Castilian to be considered the Spanish language, which it is today. However, it didn't abolish other Spanish languages.
- Catalan: The strong Catalan-Aragonese State made Catalan a language of culture, science, literature, etc. Its importance diminished for some centuries, but the desire for more autonomy for Catalonia gave it renewed importance (it never ceased to be the language of a large segment of the Catalan population), being an official language of many regions and even one state (Andorra).
- The fact that Galicia and Catalonia are in Spain makes their languages prone to Castilian influences.
- Minor languages, like Astur-Leonese, etc., became regarded as mere dialects by most people.
- Portuguese: originated from a common Galician-Portuguese language, itself originated from a common Ibero-Romance shared with Castilian (but not with Catalan), with influences from Mozarabe. Spoken by more or less 170 million people throughout the world.
- Galician: originated from a common Galician-Portuguese language, itself originated from a common Ibero-Romance shared with Castilian (but not with Catalan), with strong influence of Castilian.
- Castilian (also called Spanish): originated from a common Ibero-Romance shared with Galician-Portuguese, with some influence from Mozarabic and Basque. Spoken by more or less 300 million people throughout the world, being the second-most important international language.
- Catalan: originated from a common Romance language, separated in an early stage of development of Iberian Romance languages. Influence from Castilian (nowadays). Very similar to Occitan, it has many dialects and is spoken by about 7 million people.
- Catalan: Andorra and Spain (it is also spoken in France and Italy);
- Portuguese: many countries throughout the world;
- Spanish: many countries throughout the world.
Portuguese and Spanish are both in the ten most spoken languages in the world.