千亿 (qiān yì) is a Chinese numeral meaning 'one hundred billion' (10¹¹). It combines 千 (qiān, 'thousand') and 亿 (yì, 'hundred million'), where 亿 equals 10⁸ — so 千 × 亿 = 10³ × 10⁸ = 10¹¹. Unlike English, which uses 'billion' for 10⁹, Chinese counting follows the 'myriad system': 万 (wàn) = 10⁴, 亿 = 10⁸, 万亿 = 10¹², etc. Thus 千亿 is not 'a thousand times one billion' in the Western sense but a fixed unit in the Chinese numerical hierarchy.

This term appears frequently in contexts involving large-scale economics, national budgets, corporate valuations, population estimates, or scientific measurements — anywhere figures exceed tens of billions. It's formal and precise, used in news reports, financial statements, and policy documents. While native speakers understand it instantly, learners must remember that 亿 is the base unit for large numbers in Chinese, not 'million' or 'billion' as in English, making direct translation misleading without cultural-numerical awareness.