(a.) Tending to one point of focus; tending to approach each other; converging\.

approaching arch asymptotic banner basic bedrock capital cardinal central centralized centred centripetal centrolineal champion chief concentrated concurrent confluent confocal connivent convergent converging crowning dominant essential first foremost fundamental great headmost hegemonic indispensable leading life-and-death life-or-death magisterial main master material meeting mutually approaching of vital importance overruling paramount predominant preeminent preponderant prevailing primal primary prime principal radial radiating ranking ruling sovereign star stellar substantive supereminent tangent tangential topflight uniting vital