What is another word for "introductory"?

Roget's Thesaurus (1911) lists these synonyms for "introductory": advance, afore, aforehand, aforementioned, aforesaid, already, antecedence, antecedency, antecedent, anteposition, anterior, anteriority, anticipate, avant-courier, ball, before, beforehand, bellwether, come, coming, dance, dawn, early, ere, erewhile, eve, exordium, fashion, first, foreboding, forerun, forerunner, forestall, foreword, former, front, frontispiece, gain, get, groundwork.