The words "rate" and "ratio" are not at all interchangeable. For example, a ratio is a comparison, and it has no units of measure. It is merely a number. A rate in this context is a proportional relationship between two values, and it has measure, such as meters per second.

rate＝率 ratio= 對比

A ratio is a special kind of fraction comparing the quantity or number of two different things/persons as in the following example: The ratio of women to men in my classroom is 4:3 (or 4/3 or 4 to 3). A rate is a type of ratio that is usually used when at least one of the numbers is 1, as in a unit rate or conversion rate, as in the following examples: The unit (hourly) rate of her income is $15 per hour (per in this case means: in one). The conversion rate between inches and feet is 12 inches per foot.