Complex sentence: A mochila (pronounced "mo-chee-uh" is Spanish for knapsack, pack or pouch) is a removable lightweight leather cover put over a horse saddle for carrying mail used by the Pony Express in the nineteenth century-a type of mailbag.
Split into simpler sentences: A mochila (pronounced "mo-chee-uh" is Spanish for knapsack, pack or pouch) is a removable lightweight leather cover put over a horse's saddle. It was used for carrying mail by the Pony Express in the nineteenth century-a type of mailbag.