protasis
Webster's Dictionary (GCIDE)
Protasis \Prot"a*sis\ (pr[o^]t"[.a]*s[i^]s), n. [L., fr. Gr. pro`tasis, fr. protei`nein to stretch before, forward; pro` before + tei`nein to stretch.]
1.A proposition; a maxim. --Johnson. [1913 Webster]
2.(Gram.) The introductory or subordinate member of a sentence, generally of a conditional sentence; -- opposed to apodosis. See Apodosis. [1913 Webster]
3.The first part of a drama, of a poem, or the like; the introduction; opposed to epitasis. --B. Jonson. [1913 Webster]