Just a Dummy Variable

During calculus class, Mr. James always said "Just a dummy variable~!" when he wrote the variables inconsistently. I think he used to theta sign for angle because no matter what sign he applied at the beginning of the calculation, x, t, or y, he often turned out to write theta - unconsciously. It was funny that he often changed the variables at the middle of calculation. Actually, there're both pro and con about this. One thing good about this was that beside being concentrated, I would understand the calculation well and have a clear concept. Because if I was not clear about any of the logic, I would easily get lost whenever he changed the variable. However, it is con that changing the variables is itself very confusing. And of course, it's not good for him to keep this habit. Still, "Just a dummy variable~!" he would said.