Handbook of Descriptive Statistics/Measures of Central Tendency/Mode
Modes are the most common values in a data set.
Example: Of the data set
1, 2, 3, 4, 4, 4, 5, 6
4 is the mode because there are three responses of "4" and only one response for 1, 2, 3, 5, or 6.
Data can have more than one mode, example:
Of the data set
1, 2, 2, 3, 4, 5, 5, 6.
2 and 5 are the modes because they are equally the most frequent.
Histograms can often be a good way to see if large data sets have more than one mode.