protasis
noun
prot·a·sis ˈprä-tə-səs 
plural protases ˈprä-tə-ˌsēz
1
: the introductory part of a play or narrative poem
2
: the subordinate clause of a conditional sentence compare apodosis
protatic
prä-ˈta-tik
adjective prō-
Word History
Etymology
Late Latin, from Greek, premise of a syllogism, conditional clause, from proteinein to stretch out before, put forward, from pro- + teinein to stretch — more at thin
First Known Use
circa 1568, in the meaning defined at sense 1