The term 'historical stage' can be broken down into two crossword solutions: ERA (3 letters). An ERA is a period of time in history that is marked by certain characteristics or events. It is usually used to refer to a long period of time, such as the Middle Ages or the Renaissance. The term can also refer to a shorter period of time, such as the Victorian ERA or the Industrial Revolution. In either case, an ERA is a distinct period of time in history that is characterized by certain events or developments.