It can indicate that an event, decision, fact or environment is critical and indispensable to the result, and can determine success or failure, victory or failure. This is a crucial moment in the negotiations. His decision will be crucial to the success of the project. The evidence she presented was cruel to provide her case. The evidence she presented was crucial to prove her case. )
The word "Crucial" is usually used in formal occasions to express the importance of something and to emphasize the seriousness and urgency of something.