A crisis is something that is extremely tense with high stakes. A crisis demands immediate decisions and has serious consequences for the wrong decisions.
The plural is crises, pronounced as /cry sees/.
In medical terminology crisis has several definitions. It can be a turning point, either for better or for worse, or a severe physical or emotional change.
Someone can have a crisis of conscience if he or she has made a decision and now regrets it as immoral or against his or her sense of what is right.
Alternatively, a crisis of confidence is when others have change their opinion of a person or an organization, usually from a good opinion or a bad opinion.
An additional phrase is crisis of faith, when someone who has had strong faith in a set of beliefs begins to question the validity of those beliefs.
Those are the three most common phrases, but the term can be applied to anything that includes a drastic change in one’s thoughts or emotions, usually from good to bad.
Examples
Labour is facing one of the greatest crises in its 115-year history, according to the man who oversaw the writing of the party’s manifesto. [Herald Scotland]
As the Rohingya migration crisis draws out, meanwhile, it is quickly becoming a global crisis of conscience. [Bangkok Post]
The sense of neglect by Washington has caused a crisis of confidence among the gulf nations, capped by the announcement Sunday that King Salman of Saudi Arabia would not attend this week’s meeting — after the White House said that he would. [The New York Times]