In computer science, NP-hard problems are widely believed to be intractable, not because they have been proved so, but on the empirical evidence of no one having found a fast algorithm for any of them in over half a century of trying. But the concepts of NP-hardness and NP-completeness are themselves hard for newcomers to understand. The current American Physical Society piece Unbearable Hardness of Physics makes a common mistake when it takes **NP**-hard problems to mean problems **N**ot solvable in time **P**olynomial in the size of their input, rather than those to which *all* problems solvable in **N**ondeterministic **P**olynomial time are efficiently reducible. Come to think of it, the letters **N** and **P** also breed confusion in other fields, including our own, where **NPT** is often taken to stand for **N**egative **P**artial **T**ranspose, when it would be more correct to say **N**onpositive **P**artial **T**ranspose, admittedly a tiny imprecision compared to the confusion surrounding what **NP **means.

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