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

In a century where the lives of billions are defined by chronic disease, demographic change, and digital systems, China has become one of the central proving grounds for some of the hardest issues in global health. — Ruby Wang, semafor.com, 27 Oct. 2026

Artificial intelligence companies have been borrowing hundreds of billions of dollars, selling fresh stock, and cooking up novel and potentially risky methods of financing. — Shira Ovide, Washington Post, 27 Oct. 2026

The discovery was made by running billions of pieces of data collected by the Rubin Observatory through a search code developed by Center for Astrophysics | Harvard & Smithsonian astronomers Matthew Holman and Kevin Napier. — Adam Kovac, Scientific American, 27 Oct. 2026

Those cards generate billions of dollars a year for airlines, which make money when miles are sold to banks, which then give them to customers. — Leslie Josephs, CNBC, 27 Oct. 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