It's helpful to know what a "bear market" is, because based on history it looks like we could be here for a while.
The term on Wall Street is synonymous with serious, long-lasting declines in stock markets. In numeric terms, a bear market is a 20 percent or more drop from a recent peak.
The S&P 500 hit that milestone on Monday, dropping 20 percent from its 52-week high. Markets have stumbled through what is usually one of their best months of the year, with indexes on track for their worst December performances since 1931, during the Great Depression.
Aside from a percentage drop, there are other, more emotional ways to measure a bear market.