A millionaire is someone who has at least one million dollars in money and assets. The word can refer to someone who has a million dollars in the bank, or someone whose house, business, investments, and savings add up to a million dollars or more.

In the past, being a millionaire meant extraordinary wealth. When the word first became common in the 1800s, a million dollars could buy what 30 or 40 million dollars buys today. Millionaires were rare and lived very differently from ordinary people. Today, while a million dollars is still a significant amount of money, it's more common than before.

Someone who has many millions might be called a multimillionaire, while someone with billions is a billionaire.

Many millionaires aren't celebrities or lottery winners. They're people who lived below their means, invested their savings, and let compound interest work for them over time.