protasis

[Ancient Greek, 'pro', before + 'tasis', of action, a form of 'teinein', to stretch]

n.
1. That which is put forward; a proposition, a maxim.
2. In ancient Greek drama, the first part of a play, in which the characters and subject are introduced.
3. In grammar, the first or introductory part of a sentence, especially the clause which expresses the condition in a conditional sentence.