The detection limit is an important concept in trace analysis. However, analysts have been slow to adopt the IUPAC definition of detection limit, and as a consequence there is still a variety of usages in the current literature. The different usages can be reconciled by a proper specification of the analytical system in which the detection limit is measured. Because detection limit cannot be rigorously interpreted in terms of confidence intervals, there is little point in determining it with great precision. Nevertheless, when it is estimated by an appropriate means, it is an invaluable characteristic of an analytical system.