Amount ofornumber of?
We useamount ofwith uncountable nouns.Number ofis used with countable nouns:
We use a hugeamount of paperin the office every day.
Theamount of timeit took to finish the job was very frustrating.
A greatnumber of studentsvolunteer each year for environmental projects.
Not:A great amount of students volunteer…
I have anumber of thingsI want to talk to you about.
A quantity oforquantities of?
Quantityis more formal thanamountornumber. A quantity oforquantities ofcanbe followedby a countable noun or an uncountable noun. They are most commonly used with an adjective such ashuge, big, large, small:
The soldiers discovered a largequantity of weaponshidden under the floor of a disused building.(countable)
You only need a very smallquantity of cementto mix with the sand.(uncountable)
Largequantities of illegal drugshad been discovered.(countable)
Aid workers have delivered hugequantities of foodto the refugee camps.(uncountable)