万亿 (wàn yì) is a Chinese numeral meaning 'ten trillion' — specifically 10¹², or 1,000,000,000,000. It combines two large-number units: 万 (wàn), meaning 'ten thousand' (10⁴), and 亿 (yì), meaning 'one hundred million' (10⁸). In the Chinese numeral system, 万 × 亿 = 10⁴ × 10⁸ = 10¹², hence 万亿 denotes ten trillion — not one trillion as in some Western interpretations. This term is used exclusively for very large quantities, especially in official, financial, scientific, or statistical contexts.

You’ll commonly encounter 万亿 in reports about national GDP, government budgets, corporate valuations, or astronomical measurements — for example, China’s annual GDP is often cited in 万亿元 (trillion-yuan units). Unlike English, where 'trillion' may vary regionally (e.g., short vs. long scale), 万亿 is unambiguous in modern Standard Chinese and always means 10¹². It functions as a noun or measure word modifier and must be followed by a unit (e.g., 元, 吨, 次) or used with classifiers like 个 or 人民币.