✅ Aid and assist are both more formal and less personal words than help and imply the furthering of another’s efforts (Please assist him with the paperwork; The tea aids in digestion).
✅ Assist is better than aid when there is less need for help (assist clients; assist in planning).
✅ Aid works best when an entity like a government is helping someone or providing support for an endeavor (aid the development of programs; aid the poor).
✅ Crucial is the perfect word when discussing an extremely important decision or turning point (crucial moment; crucial issue).
✅ Crucial is sometimes interchangeable with important in situations in which the stakes are not life-and-death (The title is crucial to the success of a book).
✅ While important is more general and often appears with intensifiers like terribly and vitally, crucial is more intense on its own.