The language generally known as Spanish is more properly termed Castilian. There are several languages indigenous to Spain. Castilian just happens to be the language of the political dominant element of Spain. In addition to Castilian there are the following languages spoken in various regions of Spain:

• Basque: The language of the aboriginal inhabitants of the Iberian Peninsula now confined to the mountainous enclave on the border of Spain and France and extending into France. It is a non-Indoeuropean language with no established afiliation with any other language of the world.
• Catalan: A romance language spoken in the coastal region of northeast Spain in the which Barcelona is the principal city. It is said to have more similarity to the Provençal language spoken across the border in France. Catalonia was once an independent kingdom with an extensive trading network in the western Mediterranean. There is a Catalan-speaking enclave on the northwest coast of Sardinia.
• Galician: The romance language spoken in the northwest corner of Spain. Galician was the origin of Portuguese. It now differs somewhat from Portuguese because it is linguistically more conservative compared to the language of Lisbon which was subject to so many dynamic influence as result of Lisbon's commercial and political ties to the rest of the world.

Portuguese differs linguistically from Castilian but the difference in the written languages seems greater than it is verbally because of different spelling conventions in representing the spoken languages. The table below shows a comparison of the different ways the same sounds are depicted in Castilian and Portuguese spelling.

In some old spellings both Castilian and Portuguese use ç (c cedilla) but in modern spellings this is replaced by a z; e.g., Açores is now Azores. Likewise cabeza was once spelled cabeça.

One of the most noticable linguistic differences between Castilian and Portuguese is the presence of an initial h in Castilian in the place of an initial f in Portuguese. The f sound was in the Latin vernacular ancestor of Castilian and Portuguese but in Castilian the words with an f were pronounced with an aspirant h although they continued to be written with an f for a long period of time. Eventually the spelling replaced the f's with h's even though by that time the h-sound had disappeared in the pronunciation; i.e., the h had become silent. The reason for the disappearance of the f-sound in Castilian is probably because Castilian developed in the area where Basque was still spoken. There is no f-sound in Basque and so the Basque-speakers learning the Latin vernacular would have had an ackward time with the f-sound and would have made substitutions from their phonetic system.

There are numerous examples of cognate pairs of words in Castilian Spanish and Portuguese which differ only in the substitution of a silent h for an f.

• Fernando -- Hernando
• fazer -- hacer (to do or to make)
• falar -- hablar (to speak)