Greenback

A nickname, not a technical term. It carries no meaning distinct from the dollar itself and appears mainly in market commentary and dealer shorthand, alongside the other desk names for liquid currencies: cable for sterling against the dollar, Aussie, Kiwi and Loonie for the Australian, New Zealand and Canadian dollars. The names survive because they are unambiguous when spoken quickly over a phone line, which is where they came from.

The trap is that a sentence about the greenback strengthening is incomplete on its own. A currency has no price except against another currency, and the dollar can rise against one and fall against another within the same hour. Commentary using the single currency form usually means either the dollar's move against a basket, most often the dollar index, or its move against whichever currency is under discussion. Both readings are common and the sentence rarely says which.

One further detail catches beginners. The dollar is written as the first currency in some pairs and the second in others, so a strengthening dollar sends one quoted rate up and another down. The direction of the number on a screen describes the pair, never the dollar in isolation, which is the whole reason currency pair conventions are worth learning before the nicknames are.