This really isn’t a hidden feature, hence the speech marks, but it is a cool feature of the dictionary application that not many people know about. If you load up dictionary from applications you can access the front and back covers. If you haven’t ever picked up a dictionary before these contain some tables of elements, US presidents, abbreviations and other cool things such as how to use the dictionary.
After clicking on the Dictionary tab go to the go menu item, scroll down and click Front/Back Matter.
It is very useful and rather different. Not many people I have seen know about this, I haven’t seen it written anywhere. By the way this is a bonus tip for today since I am a bit bored, so I have decided to give you another one.