billion

number (plural billions or (with numeral or quantifying word) same)

• the number equivalent to the product of a thousand and a million; 1,000,000,000 or 10⁹:a world population of nearly 5 billion half a billion dollars
• (billions) informal a very large number or amount of something:our immune systems are killing billions of germs right now
• a billion pounds or dollars:the problem persists despite the billions spent on it
• dated, British a million million (1,000,000,000,000 or 10¹²).