When are dictionaries more useful than lists?

Q. When are dictionaries more useful than lists?

Answer =

Dictionaries can be much more useful than lists. For example, suppose we wanted to store all our friends' cell-phone numbers. We could create a list of pairs (name of friend, phone number), but once this list becomes long enough searching this list for a specific phone number will get time-consuming. Better would be if we could index the list by our friend's name. This is precisely what a dictionary does.