The term 'HISTORY CHAPTER' can be broken down into two crossword solutions: ERA (3 letters) and DECADE (6 letters). An ERA is a period of time in history that is defined by certain characteristics, such as a particular political system or cultural movement. A DECADE is a period of 10 years, and is often used to refer to a specific period in history. For example, the 1960s are often referred to as the 'Swinging Sixties' due to the cultural revolution that occurred during that DECADE.