billion

noun

bil·​lion ˈbi(l)-yən 

1

US : a number equal to 1,000 million see Table of Numbers

also, British : a number equal to 1,000 milliard see Table of Numbers

2

: a very large number

billion adjective

billionth

ˈbi(l)-yən(t)th 

adjective or noun

Did you know?

How much is a billion? It might depend on whom you ask. Billion was borrowed from French in the late 1600s to indicate the number one million raised to the power of two, or a million million—a number represented by a 1 followed by 12 zeros. However, the French later changed their naming conventions so that a billion became a thousand million (a 1 followed by 9 zeros) and a trillion became a thousand thousand million (or a million million, the old billion). The French have since returned to the older system, but it was this new system that was adopted by American English speakers in the 1800s. In Britain, the newer system has seen increasing use since the 1950s, but the older sense is still sometimes used there as well.

Examples of billion in a Sentence

We could see a billion stars in the sky.

Recent Examples on the Web

As these isotope signatures have remained unchanged for billions of years, the findings prove that extraterrestrial organic matter shares a direct, uninterrupted connection to the cosmic environment where the Solar System was born. — Mrigakshi Dixit, Interesting Engineering, 22 Sep. 2026

Why would Big Pharma kill birds worth billions of dollars when there was profit to be had? — J. B. MacKinnon, Harpers Magazine, 22 Sep. 2026

But a major new oil refinery hasn’t been built in the United States since 1977 — and banning diesel exports could be the worst way to convince the industry that now is the time to spend billions building a new one. — Matt Egan, CNN Money, 22 Sep. 2026

Nonpartisan state analysts say the tax will likely generate tens of billions of dollars, but also cost the state hundreds of millions or more in annual revenue. — Ben Paviour, Sacbee.com, 21 Sep. 2026

Word History

Etymology

French, from bi- + -illion (as in million)

First Known Use

1801, in the meaning defined at sense 2

Phrases Containing billion

• never/not in a thousand/million/billion years

Rhymes for billion

• million
• pillion
• trillion
• castilian
• civilian
• cotillion
• pavilion
• postilion
• quadrillion
• reptilian
• vermilion
• vermillion

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Kids Definition

billion

noun

bil·​lion ˈbil-yən 

1

: a number equal to 1,000 million : 1,000,000,000 see number

2

: a very large number

billion adjective

billionth

-yən(t)th 

adjective or noun