Common fraction
A common fraction is one way of expressing a fractional number. (Decimal fractions and percents are two other ways of expressing fractional numbers.)
Part of a whole or set
A common fraction may name a part of a whole or a set. 
Examples 
¾ of the pie below is left. ¾ is a common fraction naming a part of the whole pie. 



Division
Common fractions are also used to express division 
Example 
Nancy wants to make omelets for breakfast. She has 6 eggs and she needs 2 eggs for each omelet. How many omelets can she make? 

Thus, Nancy can make 3 omelets. 

Ratio
A common fraction can be used to name a ratio 
Examples 
1. Dante's birthday party included party hats and noisemakers for each guest. For each guest, there was one hat and two noisemakers. The ratio of party hats to noisemakers can be expressed as the common fraction ½ (or as the ratio 1:2). 
2. In the example below, the ratio of bees to hives can be expressed as the common fraction or as the ratio 4:1. 



Also called fraction.
See also fractions, fractional number, rational number.