Areas of pure math such as algebra, analysis, combinatorics and many others can be used—in some cases combined—to solve the complex math problems arising from applications of math to the real world.

Physicists have built a real-number version of quantum mechanics that makes all the same predictions as the standard theory, resolving a question that's simmered since the field began.

Our February Insights puzzle sent readers on a treasure hunt based on complex numbers. First we provided a bit of a primer, demonstrating that complex numbers (expressions of the form a + bi, where ...