‘纪元’ (jì yuán) literally combines ‘纪’ (jì), meaning ‘to record’ or ‘a cycle of time’, and ‘元’ (yuán), meaning ‘origin’ or ‘beginning’. Together, they form a formal noun meaning ‘era’ or ‘epoch’ — a long, historically significant period marked by a defining event or system of dating. It is most commonly used in historical, astronomical, or calendrical contexts, such as ‘公元’ (gōng yuán, Common Era) or ‘冰河纪元’ (bīnghé jìyuán, Ice Age epoch).

The term carries a scholarly or literary tone and rarely appears in casual speech. It often appears in compound nouns (e.g., ‘新纪元’ — xīn jìyuán, ‘new era’) and is frequently paired with adjectives indicating scale or significance (e.g., ‘远古纪元’, ‘数字纪元’). Unlike the more general ‘时代’ (shídài), ‘纪元’ implies a formal, often globally recognized chronological framework anchored to a foundational moment.