The value of China's currency dropped this week, with a loss of about one percent by Friday. Stories in the financial press say that is the biggest decline for the yuan against the dollar in years.
China's money is also called the renminbi, and its value is tightly controlled by Beijing.
The currency had been gaining value since 2005.
The relative value of a currency affects the economy in many ways. For example, a cheaper currency can boost the economy by making a nation's exports relatively cheap on global markets.
But a weak currency could also contribute to inflation by raising the cost of imports, such as oil.