S&P 500 enters 'bear market' — here's what that means

The S&P 500 has fallen into a bear market, an indicator that investors are worried about the economy’s future as interest rates rise.

A bear market is a term used to describe an index dropping by at least 20% from a recent high. The S&P 500, which is a basket containing 500 of the biggest U.S. companies, was down 21.3% after open on Monday from its most recent high at the beginning of the year.

The tech-heavy Nasdaq index has already been in bear market territory for quite a while. It is now down more than 31% from the start of the year. The Dow Jones Industrial Average has not yet entered into a bear market, although it was down about 2.5% on Monday and 16.3% since the start of the year.