trichotomous

adjective

tri·​chot·​o·​mous trī-ˈkä-tə-məs 

: divided or dividing into three parts or into threes

trichotomous branching

trichotomously adverb

Word History

Etymology

Late Greek trichotomein to trisect, from Greek tricha in three (akin to treis three) + -tomein (akin to temnein to cut) — more at three, tome

First Known Use

1800, in the meaning defined above