CORDILLERA, a Spanish term for a range or chain of mountains, derived from the Old Spanish cordilla, the diminutive of cuerda, a cord or rope. The name first given to certain moun tain-ranges of South America, Las Cordilleras de los Andes, was applied to the extension of the system into Mexico. In North America the Rocky Mountains, the Sierra Nevada and the moun tains between them are collectively known as the "Cordilleras," and the entire area has been termed the "Cordilleran region." The name is now not restricted to America but is often used as a gen eric term for any long parallel ranges of mountains.