The mode is a measure of central tendency in statistics that refers to the value that appears most frequently in a data set. It can be used to summarize categorical variables, while the mean and median can only be calculated for numeric variables. The mode can be calculated by counting how many times each number appears in the data set and identifying the number with the highest frequency. If there is more than one number with the highest frequency, then the data set has multiple modes. If all observed values appear the same number of times in a data set, then there is no mode. The mode is most useful as a measure of central tendency when examining categorical data, such as models of cars or flavors of soda, for which a mathematical average median value based on ordering cannot be calculated.