(a.) Pertaining to the exordium of a discourse: introductory.

agency ancestor ancestors announcer antecede antecedents antedate anterior anticipatory ascendant ascendants avant-garde base basis bellwether buccinator bushwhacker call causation cause cause and effect chief ci-devant determinant determinative earlier early elder elders element etiology exordial explorer factor fathers first fore forebear forebears forefather forefathers foregoer foregoing foremost forerun forerunner former front runner frontiersman fugleman grandfathers grandparents ground groundbreaker grounds guide harbinger heading headmost herald inaugural initiatory innovator instrumentality lead runner leader leading means messenger occasion older pace past pathfinder patriarchs pioneer point precedent preceding precessional precurrent precursor precursory predate predecessor predecessors preexistent prefatory preliminary preludial prelusive premise preparatory prevenient previous prime primogenitor principle prior proemial progenitor progenitors propaedeutic prototype reason scout senior stimulus stormy petrel trailblazer trailbreaker vanguard vaunt-courier voortrekker