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

South Africa’s energy reforms have attracted billions of dollars in committed private capital, helping to produce enough power for Eskom to end rolling power cuts that have stymied growth in Africa’s largest economy. — Tiisetso Motsoeneng, semafor.com, 12 Aug. 2026

The Legislative Analyst’s Office said the exact amount is tough to predict, but the state probably would collect tens of billions of dollars. — Queenie Wong, Los Angeles Times, 12 Aug. 2026

The prevalence of LRDs in the early universe would align with the emergence of supermassive black holes, each weighing millions to billions of suns apiece, which astronomers spy at the hearts of large galaxies. — Lee Billings, Scientific American, 12 Aug. 2026

Only weeks later, the administration had its stake, a position that is now worth tens of billions. — Sarah Polcz, Time, 12 Aug. 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