Dictionaries are reference data lists used for verifying or categorizing values against certain black- or whitelists. Dictionaries are generally enumerable and finite, whereas eg. string patterns are dynamic and evaluated each time.
Examples of meaningful dictionaries are:
A dictionary of product types like "jewelry", "menswear", "sportswear" etc.
A dictionary of gender symbols like "M", "F" and maybe "UNKNOWN".
A dictionary of age group names (eg. infant, child, young, mature, senior)
Two dictionaries for male and female given names (in order to determine gender of persons)