Mnemonics are rhymes and sayings which help us to remember facts, for example, "30 days have September, April, June and November. All the rest have 31, excepting February alone"'.
The word "mnemonic" means "a device to aid the memory" (Oxford English Dictionary). One of the most common forms of mnemonic is the rhyme, because rhymes are easier to remember than non-rhyming sayings. So in the mnemonic above, which is meant to help people remember whether a month has 31 days or not, the rhyming pairs are September/November and thirty-one/alone (you might notice this second pair is an example of approximate rhyme). It is harder to remember the number of days in each individual month than it is to remember one simple mnemonic. If it's ever the thirtieth of April and you're trying to work out the date of the following day, you'll now always know that it's the 1st of May!
Many people are not sure how to pronounce the word "mnemonic" because the mn- combination of letters is so unusual at the beginning of a word. The usual British pronunciation is: n'monic. Try our English Mnemonic quiz and see how much you remember!