Most Spanish learners will discover sooner or later two terms that refer to the same language. The election between one and another is somewhat controversial and will bring up some doubts to all the people interested in the Hispanic world. Because of this the logical question comes up, what is the right word?
To introduce the subject, let’s review the origins. The word Castilian comes from Castile, in other words one of the historic regions that form the Spanish lands. Castile is known for being the cradle of the Spanish (or Castilian) language. Castilian appeared in the Middle Ages and was based on Low Latin which also received the linguistic influence of the people present at that time in the kingdom: Arabs, Basque and Germanic-Visigoths. The language spread to all the peninsular land due to the Castile’s supremacy over other kingdoms and became the most spoken language, although some other tongues coexisted.
The conquest of the Americas resulted in the spread of the language to a large part of the continent and currently it has become the second most spoken language in the world.
Now we can see the historical origin of the word “Castilian” and understand the beginning of the divergences.
At a linguistic level, both terms are not only right, but synonyms, which means that you can use them interchangeably. The problem arises because due to political issues, there is a dispute with respect to the use of one or the other.
With regards to Spain, there are three other official languages apart from Castilian: Catalonian, Basque and Galician. Thus, to avoid giving Castilian precedence over the rest by calling it “Spanish”, it remains as “Castilian”. It is something similar to Switzerland where four official languages exit at the same time but none of them is considered “Swiss”.
In Latin America, there is a balance among the countries that use one option or the other. In the south of the continent, except for Colombia and El Salvador, the term Castilian is more widely used. It is even included in some constitutions. However in Mexico, Colombia, Central America and the Caribbean, Spanish is more likely used. The reasons to pick one or the other change depending on the way each country explains the differences between its language and “what is spoken in Spain”.
To get an official point of view, let’s see what the Panhispanic Dictionary of Doubts says about this subject:
“Spanish: To designate the common language of Spain and some American nations which is also spoken in other parts of the world, the words Castilian and Spanish are equally valid. The polemic about which of these designations is more appropriate has been left behind today. The term Spanish is more advisable because it is free of ambiguity and refers in an unequivocal way to the language which is spoken today by four hundred million people. Furthermore, it is the internationally used designation (Spanish, espagnol, Spanisch, spagnolo, etc.). While being also a synonym of Spanish, it is preferable to use Castilian to refer to the Roman dialect born in the kingdom of Castile during the Middle Ages or to the Spanish dialect spoken in that region nowadays. In Spain, that name is also used when we want to make reference to the common language of the country in relation to the rest official languages in their respective territories, like Catalonian, Galician or Basque.
Panhispanic Dictionary of Doubts, 2005, pages. 271-272”
Despite the regulatory role of this publication, I have to say that the polemic is far from having been decided. Nevertheless, what is true that Spanish learners don’t have any need of getting involved in such political questions and can use without hesitation the word “Spanish”, which is perfectly valid and universally admitted.