exordium
Concise Oxford English Dictionary © 2008 Oxford University Press:
exordium /ɪgˈzɔːdɪəm, ɛg-/
▶noun (pl. exordiums or exordia) formal the beginning or introduction of a discourse or treatise.
– derivatives
exordial adjective.
exordial adjective.
– origin C16: from L., from exordiri ‘begin’.
'exordium' also found in these Oxford entries:

