But the part that I really want to discuss here is the other part -- i.e., the phrase "if k is any constant." To most teachers, that additional phrase doesn't

But the part that I really want to discuss here is the other part -- i.e., the phrase "if k is any constant." To most teachers, that additional phrase doesn't seem important, because in the teacher's mind "x" usually means a variable and "k" usually means a constant. Most teachers get this right, using these conventions as a redundant booster to their verbal and written communication. Some are grumpy and lazy and want as much as possible to go unsaid. "For the next couple of weeks, when I say 'ring' I'm going to mean a commutative ring." Just say commutative ring. The time you save by glossing over these details doesn't add up to anything.