pivotal

Of crucial importance in relation to the development or success of something.

• pivot/ˈpɪvət/(n/v)枢轴；转向

• pivotal role
• pivotal moment
• pivotal decision
• pivotal figure
• pivotal point

1. 1.The Battle of Midway was a pivotal moment in World War II, shifting the balance of power in the Pacific. (decisive)
2. 2.She played a pivotal role in negotiating the peace agreement. (crucial)

• crucial/ˈkruːʃəl/— of great importance — very close
• decisive/dɪˈsaɪsɪv/— settling an issue — more specific
• critical/ˈkrɪtɪkl/— of the greatest importance

from "pivot" (a central point on which something turns) — the point on which everything depends