Merriam-Webster Logo
  • Dictionary
  • Thesaurus
  • Scrabble
  • Spanish Central
  • Learner's Dictionary


noun bil·lion \ˈbi(l)-yən\

Simple Definition of billion

  • : the number 1,000,000,000 : one thousand million

  • : a very large amount or number

  • : the number 1,000,000,000,000

Source: Merriam-Webster's Learner's Dictionary

Full Definition of billion

  1. 1 — see number table

  2. 2 :  a very large number




play \-yən(t)th\ adjective or noun

Examples of billion in a sentence

  1. We could see a billion stars in the sky.

Did You Know?

How much is a billion? It might depend who 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 one followed by 12 zeros. However, the French later changed their naming conventions so that a billion became a thousand million (a one followed by nine 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.

Origin and Etymology of billion

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

First Known Use: 1834

BILLION Defined for Kids


noun bil·lion \ˈbil-yən\

Definition of billion for Students

  1. 1 :  a thousand millions

  2. 2 :  a very large number <billions of stars>

Learn More about billion

Seen and Heard

What made you want to look up billion? Please tell us where you read or heard it (including the quote, if possible).