When I was a secondary school student, I used to study the subject ‘castellano’ – Castilian, in English – as part of the curriculum. At that stage it was natural for me to call ‘castellano’ the subject that studies my mother tongue, as for me ‘español’ (Spanish) and the name of the subject were the same thing.

Very often my students ask me whether there is any difference between the two terms. I usually explain that in English, Spanish is more often labeled that way, to denominate the official language of Hispanic America (Mexico, Guatemala, Peru, Cuba, Argentina, etc) and the dominant official language of Spain.

As a school subject, Spanish is generally known as ‘castellano’ in Spanish speaking countries. In English it is more often labeled ‘Spanish’. In Spanish both terms are used interchangeably when speaking about the language in general terms. However, to make reference to its nature, the term ‘Castilian’ takes precedence.

In Spain, ‘Castellano’ is used instead of ‘español’ when is necessary to make very clear that the term refers to ‘Castilian’ and not to any other of the Spanish languages such as Galician or Catalan.

Spanish can also be called ‘Castilian Spanish’ to make the distinction referred to above. Castilian as the main language of Spain has come to be identified as ‘Spanish’, a fact that is quite evident by the popularity of its usage.

Most Spanish speaking countries in South America use the term ‘castellano’ when they are referring to Spanish in general.

In strict terms, the real name of Spanish is Castilian, as this language has its roots in Castile, a region of Spain. On the other hand, ‘Spanish’, as the most popular name for this language in English, can also be used as just another name for the language of Castile. The name ‘Castilian’ is always relevant in order to study features of Spanish relating to its linguistic or historical nature.