Reserve currency
A currency held in significant quantities by central banks as part of their foreign exchange reserves. The U.S. dollar's roughly 58-60% share of global reserves (early 2020s) — down from around 70% at the turn of the millennium but still dominant — rests on self-reinforcing network effects, deep and liquid U.S. financial markets, and the Eurodollar system, giving reserve-currency status strategic as well as economic weight.