Ratio
Definition
A comparison of two quantities showing how many times one contains the other.
Explanation
Ratios can be simplified like fractions. A ratio of 2:3 means 2 parts to every 3 parts.
Example
Mixing 2 parts paint to 3 parts water gives a ratio of 2:3.
Common confusion
A ratio compares parts with parts; a fraction compares a part with the whole.