critical

Forming or having the nature of a turning point or crisis.

“a critical point in the campaign”

“the critical test”

Urgently needed; absolutely necessary.

“a critical element of the plan”

“critical medical supplies”

At or of a point at which a property or phenomenon suffers an abrupt change especially having enough mass to sustain a chain reaction.

“a critical temperature of water is 100 degrees C--its boiling point at standard atmospheric pressure”

“critical mass”

Being in or verging on a state of crisis or emergency.

“a critical shortage of food”

“a critical illness”

Characterized by careful evaluation and judgment.

“a critical reading”

“a critical dissertation”

Marked by a tendency to find and call attention to errors and flaws.

“a critical attitude”

Of or involving or characteristic of critics or criticism.

“critical acclaim”