The sell-off in stocks has reached a new level in market lingo: a correction. After tumbling in recent weeks, the Standard & Poor’s 500-stock index closed on Thursday in that territory.

What is a stock market correction?

A correction is a 10 percent drop in stocks from their peak. Since Jan. 26, the S.&P. 500 has fallen 10.16 percent.

In some ways, 10 percent is an arbitrary threshold. But it often signals that investors have turned more pessimistic about the markets.

Does this mean stocks are headed down even further?

Not necessarily.

Over the past 20 years, there have been 10 corrections in the S.&P. 500, including the current one, according to Yardeni Research. The previous correction ended in February 2016.