What is another word for mission-critical?
Pronunciation: [mˈɪʃənkɹˈɪtɪkə͡l] (IPA) 
There are several synonyms that can be used instead of the phrase "mission-critical." These include essential, vital, crucial, important, imperative, necessary, pivotal, fundamental, integral, and significant. Each of these words can be used to describe something that is absolutely necessary for the success of a certain mission or task. For example, in a medical emergency, responding quickly and efficiently is essential to saving a patient's life. In this case, the term "essential" could be used instead of "mission-critical." Similarly, an integral component of a project or system is crucial to its success. Using these synonyms can help to vary language and avoid repetition in communication.
