Translation guide
A person with a net worth of at least one billion units of a currency, typically US dollars. In Japanese, the term is often expressed with 億万長者 (okumanchōja), though this literally means 'multimillionaire' and can be ambiguous. For clarity, ビリオネア (birionea) is used, especially in modern contexts.
Referring to a person whose wealth is in the billions (of dollars, yen, etc.)
The most common Japanese term for an extremely wealthy person, literally 'millionaire of millions'. It can refer to both millionaires and billionaires, so context is needed.
He became a billionaire at a young age.
Loanword from English, specifically meaning 'billionaire'. Used in news and business contexts to avoid ambiguity.
The number of billionaires in the world continues to increase.
A person of wealth, a wealthy individual. Not specific to billionaires; can refer to anyone with substantial assets.
He is a famous wealthy individual.
Specifically a billionaire in Japanese yen (approximately 10 million USD at 100 yen to the dollar, but the term is used loosely).
In Japan, 億万長者 often implies wealth in the hundreds of millions or billions of yen. Since 1億 (oku) is 100 million, 億万 suggests multiples of that.
It's tough to become a billionaire in yen.
億万長者 is the traditional term and can be ambiguous (millionaire or billionaire). ビリオネア is a direct loanword and is unambiguous, but may sound more technical or foreign. In casual conversation, 億万長者 is more common even for billionaires.
He's a billionaire/multimillionaire.
He's a billionaire.
Do not translate 'billionaire' as 十億長者 (juuokuchouja) or similar literal constructions; these are not used in Japanese.