Mode

The mode is the simplest of all forms of central tendency.  It is simply the value that occurs most often; it is the category of most frequent response.  In the United States, for example, there are adults who have anywhere from 0 years of formal education to a doctorate.  The most common educational history, however, is to get a high school degree and no more.  12 years of education is therefore the mode.  Similarly, Protestantism is the modal religion, woman is the modal gender, English is the modal first language, and so forth.

Because the mode is simply the category with the most cases, it works best when there are few categories/values to a variable.  Therefore it is usually used with nominal or ordinal data.

SPSS instructions for finding the mode