They are not all exactly the same, no. Crucial and Indispensable mean something that you can't do without, so they are stronger than just important. They also have slightly different collocations and connotations, so we tend to use them in different contexts. Indispensable is usually applied to people or objects, whereas crucial tends to be applied more broadly, including to more abstract things like ideas or events. Note that these are both only tendencies, though. Anything that is absolutely needed can be described with either word. Prominent is the least similar. It literally means something that sticks out, like a chimney from a roof. Metaphorically, and more commonly, it means something that is noticeable, often because it is important. It's frequently used for important people, like "a prominent member of the community" or "a prominent businessman". More on reddit.com

You could say imperative in a more formal situation. More on reddit.com

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Someone else will be able to give a better answer than me, but I’ll try to explain my understanding of these words as a native speaker: Great, brilliant, marvellous, amazing, fabulous, wonderful and terrific are all the same kind of meaning to me. They can be used when something is really good at any level and for most situations. Breathtaking - This is a level above the other words and you can’t use it for every situation, I would only use this word for something that is very beautiful. For example: the view here is breathtaking. Sensational CAN be used like great - but I don’t hear it used as often in every situation - for example I would use this word to describe a really good experience, like eating food. “The curry was sensational” More on reddit.com