The number one hundred million (10^8). Used when expressing large quantities such as money or population.
その映画の興行収入は十億円を超えた。
The box office revenue for that film exceeded one billion yen.
日本の人口は約一億二千万人だ。
Japan's population is about 120 million people.
彼は投資で億単位の利益を得た。
He made profits in the hundreds of millions from his investments.