The Types of the Folktale

The American folklorist Stith Thompson translated Antti Aarne's motif-based classification system in 1928, enlarging its scope. With Thompson's second revisions to Aarne's catalogue in 1961, he created the AT-number system (also referred to as AaTh system), which is often used today, more commonly in its updated ATU number form.
The Aarne–Thompson Tale Type Index divides tales into sections with an "AT" number for each entry. The names given are typical, but usage varies; the same tale type number may be referred to by its central motif or by one of the variant folktales of that type, which can also vary, especially when used in different countries and cultures. The tale type does not have to be accurate for every folktale. For example, "The Cat as Helper" (545B) also includes tales where a fox helps the hero. Closely related folktales are often grouped within a type. For example, Tale Types 400-424 all feature Brides/Wives as the primary protagonist. For instance, "The Quest for a Lost Bride" (400) or the "Animal Bride" (402). Subtypes within a Tale Type are designated by the addition of a letter to the AT #, for instance: the "Persecuted Heroine" (510) has subtypes 510A, "Cinderella", and 510B, "Catskin".