The mode is the value in the data set that occurs most frequently.

If all of the data values occur only once, or they each occur an equal number of times, we say that there is no mode. 

If only one value occurs most often, then the data set is said to be unimodal.

If exactly two values occur equally often, then the data set is said to be bimodal.

If more than two values occur equally often, the data set is multimodal.