What is the difference between interval and ratio data?

Interval data: The data points have a uniform interval between them. E.G: Temperature. The difference between 10 and 20 degrees is exactly the same as the difference between 90 and 100 degrees. Ratio data: Almost exactly the same as interval data, except the data must have an absolute zero, meaning it is not possible for the data to be negative. E.G. Temperature is not ratio data because it is possible to have a negative value, whereas percentages on a test would be ratio data because you cannot have a negative percentage score, so there is an absolute zero.