/prot"euh sis/ , n. , pl. protases /-seez'/ .
1. the clause expressing the condition in a conditional sentence, in English usually beginning with if. Cf. apodosis .
2. the first part of an ancient drama, in which the characters are introduced and the subject is proposed. Cf. catastasis, catastrophe (def. 4), epitasis .
3. (in Aristotelian logic) a proposition, esp. one used as a premise in a syllogism.
[ 1610-20; prótasis proposition, lit., a stretching forward, equiv. to pro- PRO- 2 + tásis a stretching ( ta-, verbid s. of teínein to stretch + -sis -SIS) ]