Together with other initially European languages such as Portuguese, French or Italian, the linguistic roots of Spanish make it a Romance language. This means that Latin, or more specifically, Vulgar Latin, constitutes its most important linguistic base.

The constant contact and mutual influence of the Latin basis with other linguistic traditions and cultures has led to the formation of the different Romance languages as we know them today. In the case of Spanish, there are, for example, characteristics that come from the Iberian and Celtic traditions.

There is also a great amount of Greek vocabulary that was first adopted by Latin speakers and then brought into Spanish. Words such as "escuela" (school) or "huerfano" (orphan) all belong to this tradition. And we should not forget the seven centuries of Arab domination of the peninsula. This has left, among other things, an important legacy of lexical elements that have been incorporated into the Spanish language. A surname you probably know which exemplifies this is "Almodovar".

Spanish is, especially in the bilingual territories of Spain, also known as castellano (Castilian), because of its origins in the region of Castilla. Castilla is situated in the north-central part of Spain, and it was once the neuralgic center of the Spanish empire that would take the Spanish language to more than twenty other countries.

The establishment of a linguistic unity of Spanish as a common language for the state of Spain was parallel to its territorial unity. This union was only possible after the Reconquest of the peninsula from the Arab settlers, at the end of the 15th century. The kingdom of Castilla, and also its linguistic variety, expanded to the practical totality of the Iberian Peninsula. After the marriage of Isabel I of Castilla and Fernando II of Aragon, the Spanish state was born, and Castilian language and culture became its most dominant identity. During the sixteenth and seventeenth centuries, through a series of linguistic evolutions and normalizing changes, the language of the Spanish state became what is nowadays known as Modern Spanish.

It is important to remember, however, that spoken Spanish is not identical in the different regions of the Spanish state. In fact, its pronunciation and lexical characteristics can vary to a very significant extent from one place to another. However, the maintenance of a unified, standard, version of the Spanish language and of its written form is guaranteed by the Real Academia de la Lengua Espanola. The Academia sets the rules to follow in order to speak and write in a way that is accepted by all the different Spanish speakers.