One of these will help you to remember difficult things…

And the correct answer is a mnemonic. Some things are easier to forget than others. That's why we have mnemonics. From the Greek word mnemon (remembering), a mnemonic is a useful trick that helps you to recall a difficult formula or sequence of words.

 Every English schoolchild's favourite is probably "Richard Of York Gave Battle In Vain," which gives us the colours of the rainbow: Red, Orange, Yellow, Green, Blue, Indigo, Violet. There's also the points of the compass: "Never Eat Soggy Waffles" for North, South, East and West.

In the United States, HOMES helps people to remember the names of the Great Lakes: Huron, Ontario, Michigan, Erie, Superior.