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billion Syllabification: bil·lion
Pronunciation: /ˈbilyən/

Definition of billion in English:

cardinal number (plural billions or (with numeral or quantifying word) same)

1The number equivalent to the product of a thousand and a million; 1,000,000,000 or 109: a world population of over 6 billion half a billion dollars
More example sentences
  • They export more than three and a half billion dollars worth of liquefied natural gas a year.
  • Measurements of infrared light reveal that the black hole has a mass equivalent to three billion suns.
  • In this case four big donors get big contracts of between half a billion and two billion dollars.
1.1 (billions) informal A very large number or amount of something: our immune systems are killing billions of germs right now
More example sentences
  • Massive arcologies looming in the distance, like small mountains covered in billions of tiny lights.
  • Only one surviving bacterium or virus could multiply into billions in no time.
  • A vegetarian diet would drastically reduce the amount of crop land needed to feed billions.
1.2A billion dollars (or pounds, etc.): the problem persists despite the billions spent on it
More example sentences
  • Throughout that month, the Bank of England spent billions ensuring the pound stayed within its ERM band.
  • It would be the best two and a half billion ever spent for the legacy an Olympics would give to British sport.
  • About half a billion in tax and lottery money has been poured into British sport over the past four years.
1.3 dated, chiefly British A million million (1,000,000,000,000 or 1012).
Example sentences
  • 1,000,000,000,000: Trillion. An old British tradition calls this a Billion
  • A conventional British billion is a thousand times bigger than an American billion.
  • The 'old' billion was 1000,000,000,000; this is now the trillion.


Pronunciation: /ˈbilyənTH/
ordinal number
Example sentences
  • The devices play nice with each other, the way routers do on the Internet - your transmitter will check and if this particular frequency is not being used for the next 50 billionths of a second by another device, it'll send its data out on it.
  • But tumors, hormonal and reproductive problems have only appeared in rodents at extremely high, daily doses - in several grams per kilogram, not billionths of grams.
  • Researchers envisage a time when tiny machines no more than a few billionths of a metre across surge though our bodies to deliver drugs and destroy disease-causing pathogens.


Late 17th century: from French, from million, by substitution of the prefix bi- 'two' for the initial letters.

Words that rhyme with billion

jillion, million, bajillion, modillion, multibillion, multimillion, pillion, septillion, sextillion, squillion, trillion, zillion
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