The language known today as Spanish is derived from a dialect of spoken Latin that evolved in the north-central part of the Iberian Peninsula after the fall of the Western Roman Empire in the fifth century. A written standard was developed in the cities of Toledo (13th to 16th centuries) and Madrid (from the 1560s). Over the past 1,000 years, the language expanded south to the Mediterranean Sea, and was later transferred to the Spanish colonial empire, most notably to the Americas. Today it is the official language of 21 countries and of numerous international organizations. It is also one of the six official languages of the United Nations.

Se denomina etimología al estudio del origen de las palabras, de la cronología de su incorporación a un idioma, así como de la fuente y los detalles de sus cambios estructurales (de «forma») y de significado.