ERAS

An era is a broad span of time recognized for its distinctive characteristics, events, or developments. The concept is used across disciplines such as geology, history, archaeology, and cultural studies to organize the past into understandable segments. Eras are not fixed universal lengths; their boundaries are defined by consensus or significant changes rather than a strict clock.

In geology, an era is a formal division of an eon and contains multiple periods. The Phanerozoic eon is divided into the Paleozoic, Mesozoic, and Cenozoic eras, each marked by major life-forms and environmental shifts. Earlier eons and eras are defined with varying precision, and regional stratigraphy can differ.

In historical and cultural contexts, eras describe broad stretches characterized by shared features such as political systems, technologies, or cultural practices. Examples include the Classical era of ancient Greece and Rome, the Medieval era in Europe, the Renaissance and Early Modern era, and the Modern era. In non-Western histories, eras reflect regional frameworks such as Chinese dynastic or Imperial eras. These periods are often analytic constructs and their exact start and end dates can be debated.

Eras help scholars compare long-term changes, such as transitions from hunting-gathering to agrarian societies, or from empires to nation-states, or from analog to digital technology. They also appear in common usage, like the Industrial Era or the Information Era, though such modern labels can be fluid and contested.

Related concepts include period, epoch, and age, which denote smaller or more specific intervals within or across eras.