extremely largea vast amount/number/quantity: Our dog eats a vast amount of food each day.
a vast range/array: the vast array of computer games available
in vast numbers/amounts: People flocked to the show in vast numbers.
the vast majority of (=almost everyone or everything): I believe the vast majority of people (=almost everyone) will support us.
a vast expanse (=a very large area): the vast expanse of the National Park