Prŏt'a-sĭs, n.

noun

n. [Lat., Gr. πρότασις, from προτείνειν, to stretch before, forward, from πρό, before, forward, and τείνειν, to stretch; Fr. protase.]

A proposition; a maxim. Johnson.
(Gram.) The subordinate member of a sentence, generally of a conditional sentence;—opposed to apodosis.
(Anc. Drama.) The first part of a comic or tragic piece, in which the several persons are shown, their characters intimated, and the subject proposed and entered on.