ex·or·di·um 
(ĭg-zôrdē-əm, ĭk-sôr-)
(ĭg-zôrdē-əm, ĭk-sôr-)n. pl. ex·or·di·ums or ex·or·di·a (-dē-ə)
A beginning or introductory part, especially of a speech or treatise.
[Latin, from exōrdīrī, to begin : ex-, intensive pref.; see EX- + ōrdīrī, to begin; see ar- in the Appendix of Indo-European roots.]
ex·ordi·al adj.