trichotomy
Concise Oxford English Dictionary © 2008 Oxford University Press:
trichotomy /trʌɪˈkɒtəmi, trɪ-/
▶noun (pl. trichotomies) a division into three categories.
– derivatives
trichotomous adjective.
trichotomous adjective.
– origin C17: from Gk trikha ‘threefold’, on the pattern of dichotomy.
'trichotomy' also found in these Oxford entries:

