IPA: /ˈhɛp.tɑːrk/
KK: /ˈhɛpˌtɑrk/
A ruler or leader of a group of seven, especially in a historical or political context.
The heptarch was responsible for governing the seven regions of the kingdom.
Heptarch is formed from "hepta-" (from Greek "heptá", meaning seven) and "arch" (from Greek "archē", meaning rule or government). The word refers to a government or rule by seven leaders or authorities.
Think of 'hepta-' meaning seven and 'arch' meaning rule — so a heptarch is a ruler among seven.