To get an understanding of the ratio scale, there needs to be an understanding of the interval scale. The interval scale has the intervals between each measurement increment equally split. Think of the temperature on a thermometer. The difference between 71 degrees and 72 degrees is the same as the difference between 31 and 32 degrees. The increments are in even intervals.
The ratio scale is an interval scale, but it does have a true zero point. Consider weight. There could be zero weight (none). The difference between four inches and five inches is the same as the difference between 72 inches and 73 inches, so in the ratio scale it is a type of an interval scale. The difference is the ZERO as a possibility. A thermometer has a zero, so how is that different? The zero on Fahrenheit scale or the Celsius scale is not a true zero point. Instead, the zero is a reference point to separate temperatures above and below zero. True zero, means no temperature at all. If the theory of absolute zero is true where there is no heat, such as in deep outer space, then the thermometer would be a ratio scale.
