Exponential Four Clans

The Exponential Four Clans is the nickname given to the four families that are well known in the locale where the Hyouka series is set. The nickname is based on the first characters of each family's surname, which are composed of kanji for numbers (十 or 10 for Juumonji, 百 or 100 for Sarusuberi, 千 or 1,000 for Chitanda, and 万 or 10,000 for Manninbashi).
 * Juumonji Family (十文字) of the Arekusu Shrine - Known as the family that runs the Arekuru Shrine, which also holds the annual Living Doll Festival. Represented at Kamiyama High School by Kaho Juumonji.
 * Sarusuberi Family (百日紅) of the Small Shrines
 * Chitanda Family (千反田) of Wealthy Farmers - Famous for their flourishing agricultural business and is considered a traditional Japanese family. Eru Chitanda comes from the Chitanda family.
 * Manninbashi Family (万人橋) of the Mountain Owners

Trivia

 * Only the Juumonji and Chitanda families have appeared in the story. The Hyouka Drama CD, however, has featured a female Sarusuberi character and a male Manninbashi character talking to Masashi Toogaito, which may imply that there are students in Kamiyama High School that belong to either of the two remaining clans.