billion

American  

[bil-yuhn] / ˈbɪl jən /

noun

billions, plural billion plural

1. a cardinal number represented in the U.S. by 1 followed by 9 zeros, and in Great Britain by 1 followed by 12 zeros.

2. a very large number.

   I've told you so billions of times.

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adjective

1. equal in number to a billion.

billion British  

/ ˈbɪljən /

noun

1. one thousand million: it is written as 1 000 000 000 or 10 ⁹

2. (formerly, in Britain) one million million: it is written as 1 000 000 000 000 or 10 ¹²

3. (often plural) any exceptionally large number

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determiner

1. (preceded by a or a cardinal number)

   1. amounting to a billion

      it seems like a billion years ago

   2. ( as pronoun )

      we have a billion here

Other Word Forms

Derived Forms

• billionth
  adjective

Inflected Forms

Nouns

• billion
  plural
• billions
  plural

Etymology

Origin of billion

1680–90; < French, equivalent to b ( i )- bi- ¹ + -illion, as in million

Compare meaning

How does billion compare to similar and commonly confused words? Explore the most common comparisons:

• billion vs. trillion

Explanation

A billion is 1,000,000,000. There are over 7 billion people in the world, the last time we checked. While billion may sounds like a made-up number like zillion — which just means a lot — it's a very real number, specifically 1,000,000,000. That's a pretty hard number to imagine, but one way to think of it is as a thousand millions. If you have a billion dollars, you're very rich: a billionaire. Money spent by the government is often measured in billions. In England, this word often refers to a different number: 1,000,000,000,000, or one million millions.

Example Sentences

According to the researchers, these reorganized surfaces reduce oxygen reactions by a factor of a billion to a trillion.

From Science Daily • Jul. 12, 2026

The United Nations Office for Disaster Risk Reduction estimates losses of almost $37 billion in material damage alone.

From Barron's • Jul. 11, 2026

Within that, zero-sugar sports drinks had sales of $2.1 billion, a 4% year-over-year gain.

From MarketWatch • Jul. 11, 2026

Despite these efforts, which were implemented alongside the government's baby-boosting programmes that have cost about $250 billion since 2006, birth rates continued to fall for years.

From BBC • Jul. 10, 2026

That means the 10 billion neurons in your brain and spinal cord have a possible 10 trillion synaptic choices to make.

From "Phineas Gage" by John Fleischman