亿万 (yì wàn) is a compound numeral meaning 'hundreds of millions' or, more loosely, 'countless' or 'innumerable'. It combines 亿 (yì), meaning '100 million', and 万 (wàn), meaning '10,000'; together they form an emphatic, large-scale quantity—not a literal multiplication (100 million × 10,000), but rather a rhetorical intensifier suggesting vastness beyond precise counting.

This term appears frequently in formal, literary, or journalistic contexts—especially when describing populations, historical time spans, natural phenomena, or abstract concepts like effort or possibilities. It conveys magnitude and awe, not mathematical precision. While it can modify nouns directly (e.g., 亿万人民), it often functions as an adjectival phrase before a noun and rarely stands alone as a subject or object without context.