Addiction medicine

The sixteenth entry is o diagnóstico duplo, and the trap for an English reader is that the obvious word is the wrong one. Portuguese covers the whole field with duplo, while English splits it between « double » and « dual », and the two are not interchangeable. « Double » is arithmetic: twice the amount, or a second copy of the same thing — a double whisky, a double room, a double check, double vision. « Dual » is structural: one thing made of two parts that work together — dual carriageway, dual nationality, dual control, dual-purpose. The term here belongs firmly to the second group, because nobody is diagnosed twice over. One condition is psychiatric and the other is a substance disorder, and the whole point of the phrase is that they have to be handled as a single situation, which is exactly what the example sentence says about the two teams. Written as « double diagnosis » it reads as a diagnosis made a second time, a clerical matter rather than a clinical one. The same fork runs through the nouns: « a duality » is a structure, whereas « a double » is a stand-in.