protasis

noun

1. The first part of a play, in which the setting and characters are introduced.

   “It doubles itself in the middle of his life, reflects itself in another, repeats itself, protasis, epitasis, catastasis, catastrophe.”

2. A clause that expresses a contingent element in a conditional sentence.

   “In "I will be coming if this weather holds up", "if this weather holds up" is the protasis, and "I will be coming" is the apodosis.”

   “2005 B. P. Bairan: An Introduction to Syllogistic Logic Every conditional statement is made up of two component statements. The component statement that follows the "if" is called antecedent (or the "implicans" or — rarely — the "protasis"), and the component statement that follows the "then" is the "consequent"(or the "implicate" or — rarely — the "apodosis").”