How do you use "crucial', "vital" and "essential" ?
I'm not sure to chose which one when I try to express the meaning of "very important".
Thank you so much if you can help me to figue it out. :P

Question

How do you use "crucial', "vital" and "essential" ?
I'm not sure to chose which one when I try to express the  meaning of "very important".
Thank you so much if you can help me to figue it out. :P

Answer

Here is what I wrote about 'vital' (comparing it to 'important'):
"Something important has high significance, but something vital is absolutely necessary.

Ex.
Your arms and legs are very important, but your heart and brain are vital."
http://www.italki.com/question/197328

All three of the words you mentioned have the same meaning. 'Essential' doesn't sound as strong as the other two because it's used far more often, but that's it.

Answer

They're very similar. It's just a matter of degree and timing. I think examples will explain best.

Important.
If you want to get a good job, it is essential that you get a good education first.
When you go on a long hike, it is essential to bring plenty of water.

Extremely important/time critical.
If you are bitten by a rattlesnake, it is vital/crucial that you get to a hospital immediately.

Answer

They're all pretty much the same.