億

A phono-semantic compound composed of:

人 — semantic component (related to counting or human context);

意 — phonetic component indicating the sound (억 / yì).

Originally, 億 meant "to be at ease" or "comfortable," coming from the idea of a person (人) whose will or intentions (意) go according to plan. However, through phonetic loan, it came to be used exclusively to mean the number "one hundred million", and that is its primary use today.
Semantic development: - large, indefinite number; - standardized as 100,000,000; - figuratively: countless; immense.

억만 (億萬) — hundreds of millions; countless

수억 (數億) — several hundred million

억대 (億臺) — worth hundreds of millions (e.g., price range)

億 is a key unit in the East Asian numbering system, where numbers are grouped by ten-thousands (万) rather than thousands (千). It is widely used in finance, population statistics, and large-scale measurements across Chinese, Korean, and Japanese contexts.
Related characters: 萬 — ten thousand

千 — thousand

兆 — trillion (in modern usage, varies by system)