tetrarch
noun
te·trarch ˈte-ˌträrk 
ˈtē-
1
: a governor of the fourth part of a province
2
: a subordinate prince
tetrarchic
te-ˈträr-kik
adjective tē-
Word History
Etymology
Middle English, from Latin tetrarcha, from Greek tetrarchēs, from tetra- + -archēs -arch
First Known Use
12th century, in the meaning defined at sense 1