Definition of: protasis

(prot′ə·sis) noun
1. In a conditional sentence, the clause (usually introductory) that contains the condition or antecedent: distinguished from apodosis.
2. The introductory or subordinate clause in a sentence not conditional.
3. In classical drama, the introductory part of a play. [<LL <Gk., a hypothesis <pro- before + teinein stretch]