One has claws at the end of its paws, and one is a pause at the end of a clause.
A linguistics professor was lecturing to his English class one day. “In English,” he said, “a double negative forms a positive. In some languages, though, such as Russian, a double negative is still a negative. However, there is no language wherein a double positive can form a negative.”
A voice from the back of the room piped up, “Yeah, right.”