The term for a period of 100 years is a century. Centuries are commonly used in historical contexts to group events or developments according to their chronological significance. For example, the 20th century refers to the years from 1901 to 2000. Centuries can be further divided into decades, which consist of ten years, allowing for a more granular examination of time and progress within specific areas such as culture, science, and technology. In both academic and casual discussions about history, decades and centuries provide a helpful framework for understanding changes and trends over long periods.