In the twentieth century, Spanish was introduced to Equatorial Guinea and the Western Sahara, and to areas of the United States that had not been part of the Spanish Empire, such as Spanish Harlem in New York City.
For details on borrowed words and other external influences upon Spanish, see Influences on the Spanish language.
In modern Spanish, there is no difference between the pronunciation of orthographic b and v, with some exceptions in Caribbean Spanish.
Peculiar to Spanish (as well as to the neighboring Gascon dialect of Occitan, and attributed to a Basque substratum) was the mutation of Latin initial f into h- whenever it was followed by a vowel that did not diphthongize.
Compare the examples in the following table: From the sixteenth century onwards, the language was taken to America and the Spanish East Indies via Spanish colonization of America.
Miguel de Cervantes Saavedra, author of Don Quixote, is such a well-known reference in the world that Spanish is often called la lengua de Cervantes ("the language of Cervantes").
This distinctive dialect spread to southern Spain with the advance of the , and meanwhile gathered a sizable lexical influence from the Arabic of Al-Andalus, much of it indirectly, through the Romance Mozarabic dialects (some 4,000 Arabic-derived words, make up around 8% of the language today).
The loanwords were taken from both Classical Latin and Renaissance Latin, the form of Latin in use at that time.
According to the theories of Ramón Menéndez Pidal, local sociolects of Vulgar Latin evolved into Spanish, in the north of Iberia, in an area centered in the city of Burgos, and this dialect was later brought to the city of Toledo, where the written standard of Spanish was first developed, in the 13th century.
The first documents to show traces of what is today regarded as the precursor of modern Spanish are from the 9th century.
Throughout the Middle Ages and into the modern era, the most important influences on the Spanish lexicon came from neighboring Romance languages—Navarro-Aragonese, Leonese, Catalan, Portuguese, Galician, Occitan, and later, French and Italian.