billion, B (billion)

The word billion refers to a thousand million (10⁹ or 1,000,000,000). In British usage, billion historically referred to a million million (10¹² or 1,000,000,000,000), as you may see in older texts. But since 1974, British usage has mirrored North American usage.

Where billion is qualified or preceded immediately by a number, do not use the plural form billions.

• The new bridge cost over $4 billion to build.
• There are now more than six billion people living on our planet.

BUT

• There are billions and billions of stars in the sky.
• Hundreds of billions of dollars were spent in preparation for the millennium bug.

Also, the abbreviation B for billion—found in newspapers especially—should not be used in formal writing. Note that there is no space between the number and the letter (e.g. 5B), whereas there is a space between the number and the word.

• Informal: Federal aid was reduced by $2.3B in the budget.
• Formal: Federal aid was reduced by $2.3 billion in the budget.