Our group had some confusion about preparing spells for a Wizard and Cleric. The rules say that you prepare a number of spells from your list and that you tick off spell slots when you cast a spell. In D&D 3.x, if you wanted to cast a spell multiple times you had to prepare it multiple times, but we couldn't figure out from the rules whether or not this was the case in D&D 5e. 

So can a spell be prepared once and then cast multiple times?