Which of the following is not a synonym of the word "fatal"? 

The word "fatal" typically refers to something causing death or leading to disastrous consequences. Let's examine each option:

1. Deadly: This is a synonym of "fatal" as it also means causing or able to cause death.

2. Vital: This is not a synonym of "fatal." "Vital" means essential or necessary for life, which is the opposite of "fatal."

3. Lethal: This is a synonym of "fatal" as it means causing death or capable of causing death.

4. Destructive: While "destructive" can imply causing harm or damage, it does not specifically denote causing death. Therefore, it's not a direct synonym of "fatal."

In summary, "vital" is not a synonym of "fatal" as it has the opposite meaning. The other options, "deadly," "lethal," and "destructive," are synonyms of "fatal" as they all relate to causing death or harm.