Mnemonics (pronounced “ne-mon’-ics") assist the memory, using a system of rhymes, rules, phrases, diagrams, or acronyms. These devices help to remember, memorize, and recall information such as names, dates, facts, or figures. They do that by turning original information into an easy, more appealing rhyme or sentence. This can be stored in your brain as an easy reference for larger “meaningful" chunks of data. When you need to recall the original facts you can, by translating the mnemonic memory.

For example: “Roy G Biv" helps you reproduce the names and order of the colors of the rainbow. Every letter stands for a color (i.e., R for Red, O for Orange, etc.).
The order is preserved by the somewhat meaningless sentence Roy G Biv.
For some reason, we as humans remember relatively nonsensical combinations even better than we retain the complete, original information.

In Summary

– The information is translated into “meaningful" parts (chunked)
– Then it is stored in our brain
– Once recalled (remembered) it can be re-translated into the original data

Variations

Other names for a mnemonic device are memory tool, memorization aid, aid to memory, memory device, learning device, learning trick, or brain tool. They are all names for the same thing, an easy way to help use your memory, or memorize, more effectively.

There is even a mnemonic for spelling the word “mnemonic."

Interesting Fact

Sometimes it’s confused with a pneumonic device, which is medical equipment used to help with respiratory problems.

From Wikipedia
A mnemonic (pron.: /nəˈmɒnɨk/,[1] with a silent “m”), or mnemonic device, is any learning technique that aids information retention. Mnemonics aim to translate information into a form that the human brain can retain better than its original form. Even the process of applying this conversion might already aid the transfer of information to long-term memory. Commonly encountered mnemonics are often for lists and in auditory forms, such as short poems, acronyms, or memorable phrases, but mnemonics can also be for other types of information and in visual or kinesthetic forms. Their use is based on the observation that the human mind more easily remembers spatial, personal, surprising, physical, sexual, humorous, or otherwise “relatable" information, rather than more abstract or impersonal forms of information.

The word mnemonic is derived from the Ancient Greek word μνημονικός (mnēmonikos), meaning “of memory”[2] and is related to Mnemosyne (“remembrance”), the name of the goddess of memory in Greek mythology. Both of these words are derived from μνήμη (mnēmē), “remembrance, memory.”[3] Mnemonics in antiquity were most often considered in the context of what is today known as the Art of memory.
Ancient Greeks and Romans distinguished between two types of memory: the “natural" memory and the “artificial" memory. The former is inborn and is the one that everyone uses automatically and without thinking. The artificial memory in contrast has to be trained and developed through the learning and practicing of a variety of mnemonic techniques.
Mnemonic systems are special techniques or strategies consciously used to improve memory; it helps employ information already stored in long-term memory to make memorization an easier task

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