1.
one hundred million (100,000,000)
The number 100 million; a fundamental unit in the Japanese number system.
Counting patterns
Japanese groups large numbers by four digits, not three: 万 is 10,000 and 億 is 100,000,000 (一万 × 一万). So 十億 is one billion, and 兆 is one trillion.
Watch out
Converting to English, count the zeros: 三億円 is 300 million yen.
Cultural note
一億 long stood for the whole population of Japan, as in 一億総〜 ("all hundred million"): the wartime slogan 一億玉砕 and the postwar phrase 一億総中流 (everyone is middle class).