Protasis /(prŏt"ȧ*sĭs)/

Prot·a·sis

Protasis

n.
  1. A proposition; a maxim.
  2. The introductory or subordinate member of a sentence, generally of a conditional sentence; -- opposed to apodosis. See Apodosis. (Gram.)
  3. The first part of a drama, of a poem, or the like; the introduction; opposed to epitasis.