Confucius pointed out that the first step toward wisdom is calling things by the right name. The term "Differential Item Functioning" (DIF) did not arise fully formed from the miasma of psychometrics, it evolved from a variety of less accurate terms. Among its forebears was "item bias" but that term has a pejorative connotation that does not always apply to DIF; also, bias requires an external criterion, whereas DIF is an internal measure. This is roughly analogous to the distinctions between validity and reliability. One proposed term, "Differential Item Performance", had all the characteristics desired, but the acronym DIP caused concern. And so "Functioning" replaced "Performing" and DIF was born. The authors' point here is to note that the name "Differential Item Difficulty" (DID) was never seriously considered. DIF is a broader concept. The authors are concerned if an item functions differently in two groups, and that concern is manifest if the differential performance is in difficulty, in discrimination, or in other aspects that might be more difficult to characterize. However, all of these possible ways for differential performance are not of equal concern. Difficulty is certainly the most important, with the others stringing along behind. In this article, the authors discuss the most commonly used method for detecting DIF, the Mantel-Haenszel statistic (MH), which focuses all of its power on a single parameter that measures the difference in difficulty. They also discuss how the efficacy of other methods can be evaluated.