Cordillera vs. sierra vs. cadena montañosa
The Spanish words 'cordillera', 'sierra', and 'cadena montañosa' all refer to a series or chain of mountains, but with slight differences in use and connotation. These words are not always interchangeable as they sometimes apply to specific geographical features.
Cordillera
A system of mountain ranges, often consisting of parallel or connected ranges.
La cordillera de los Andes es la más larga del mundo.
(The Andes mountain range is the longest in the world.)
La cordillera Himalaya contiene muchas de las montañas más altas del planeta.
(The Himalayan mountain range contains many of the highest mountains on the planet.)
Sierra
Refers to a mountain range, often with a serrated or jagged appearance, much like a saw blade (which is 'sierra' in Spanish).
La Sierra Nevada en España es famosa por sus impresionantes vistas y oportunidades para practicar deportes de invierno.
(The Sierra Nevada in Spain is famous for its stunning views and winter sports opportunities.)
La sierra de Guadarrama es una parte importante del sistema Central.
(The Guadarrama mountain range is an important part of the Central system.)
Cadena montañosa
'Cadena' translates directly as 'chain', so 'cadena montañosa' is a linked series or chain of mountains. It can be used more generally to mean any series of mountain ranges.
La cadena montañosa del Himalaya incluye el Everest, la montaña más alta del mundo.
(The Himalayan mountain chain includes Everest, the highest mountain in the world.)
Los Alpes forman una impresionante cadena montañosa en Europa central.
(The Alps form an impressive mountain chain in central Europe.)
Summary
'Cordillera', 'sierra', and 'cadena montañosa' can all be translated as 'mountain range' or 'chain of mountains' but they are used slightly differently. ‘Cordillera’ has a very grand scope and refers to large complex systems often made up of parallel or connecting ranges like the Andes. ‘Sierra’ tends to describe more jagged or serrated-looking ranges, like a saw blade, which is what 'sierra' means. ‘Cadena Montañosa’ can be used more generally for any series or chain of mountains.