PIVOTAL

pivotal, polar

(adjective) being of crucial importance; “a pivotal event”; “Its pivotal location has also exposed it to periodic invasions”- Henry Kissinger; “the polar events of this study”; “a polar principal”

Source: WordNet® 3.1

Etymology

Adjective

pivotal (comparative more pivotal, superlative most pivotal)

Of, relating to, or being a pivot.

Being of crucial importance; central, key.

Source: Wiktionary

Piv"ot*al, a.

Definition: Of or pertaining to a pivot or turning point; belonging to, or constituting, a pivot; of the nature of a pivot; as, the pivotalopportunity of a career; the pivotal position in a battle.

Source: Webster’s Unabridged Dictionary 1913 Edition