A single number tracking the dollar's strength against a basket of other major currencies.
The US Dollar Index measures the dollar's value against a weighted basket of other major currencies, the euro carries the biggest weight, followed by the yen, pound, and a few others, so instead of asking "is the dollar strong against the euro" or "against the yen" separately, DXY gives one number for "is the dollar broadly strong or weak." A rising dollar makes imports cheaper for Americans but makes US exports and American company earnings abroad worth less once converted back to dollars, which is why a big DXY move gets its own headline even on days nothing else obvious happened.
Part of the Open Bell Glossary — plain-English explanations of the terms that come up on the show. Browse every term.