A mnemonic (Pronounced in American English, [nəˈmɒnɪk] in British English) is a memory aid. Mnemonics are often verbal, are sometimes in verse form, and are often used to remember lists. Mnemonics rely not only on repetition to remember facts, but also on associations between easy-to-remember constructs and lists of data, based on the principle that the human mind much more easily remembers data attached to spatial, personal or otherwise meaningful information than that occurring in meaningless sequences. The word mnemonic shares etymology with Mnemosyne, the name of the titan who personified Memory in Greek mythology.
One common mnemonic device for remembering lists consists of an easily remembered word, phrase, or rhyme whose initials or other characteristics are associated with the list items. The idea lends itself well to memorizing hard-to-break passwords as well.
Science and technology
The name Roy G. Biv helps us to remember the order of the colors in the spectrum. In England "Richard Of York Gave Battle In Vain" is popular (Red, Orange, Yellow, Green, Blue, Indigo, Violet). In an alternate version, "Battle" is replaced with "Birth".
A mnemonic to remember which way to turn common (right handed) screws and nuts, including light bulbs is "Lefty loosey, righty tighty."
A mnemonic used by physics students to remember the Maxwell relations in thermodynamics is "Good Physicists Have Studied Under Very Fine Teachers", which helps them remember the order of the variables in the square, in clockwise direction. Another mnemonic used here is "Valid Facts and Theoretical Understanding Generate Solutions to Hard Problems", which gives the letter in the normal left to right writing direction.
Chemistry students use the phrase "LEO says GER" to keep the two halves of a redox process straight, since the Loss of Electrons is Oxidation while the Gain of Electrons is Reduction. Another version is the word "OIL-RIG", meaning Oxidation Is Loss, Reduction Is Gain (of electrons).
The Group VIII inert gases (helium, neon, argon, xenon and radon) may be recalled by the sentence "Heaven Never Arsked Kriegspiel's eXtra Rent"
Stellar classification uses a peculiar group of letters, easily remembered using the phrase, "Oh Be AFine Girl, Kiss Me Right Now Sweetie."
For naming the planets in order from the Sun, the phrases: "My Very Easy Memory Jingle Seems Useful Naming Planets", "Man Very Early Made Jars Stand Up Nearly Perfect", and My Very Eager Mother Just Served Us Nine Pizzas."
Many mnemonics have been devised for remembering the digits of pi, consisting of phrases or verses in which successive digits of pi are obtained by counting the number of letters in each word. (Fortunately, the first thirty digits of pi contain no zeroes). Some are:
"May I have a large container of coffee?" (May = 3, I = 1, have = 4, etc.)
"May I have a large container of orange juice?"
"How I want a drink, alcoholic of course, after the heavy lectures involving quantum mechanics!"
(Alternate version of previous) "How I need a drink, alcoholic in nature, after the heavy lectures involving quantum mechanics!"
"Red, right, return," used to remember which sea mark denotes which side of a sailing channel.
The phrase "Bad Boys Rape Our Young Girls But Violet Gives Willingly" but is used to remember the electronic color codes of resistors, capacitors and other electronic components. A milder version is "Bright Boys Rave Over Young Girls But Veto Getting Wed."
"King Xerces Can Seduce Lovely Princesses" aids in remembering the microwave frequency bands, in order of increasing wavelength.
A well-known mnemonic used to remember the 12 cranial nerves uses no profanity but isn't politically correct: "Oh Oh Oh, To Touch And Feel A Girl, Very Sexy & Hot." The clean version is making ground though, and it goes like this: "On Old Olympus' Tiny Top AFinn And German Viewed Some Hops," or "On Old Olympus' Towering Top AFinely Vested German Viewed AHawk" (with variations; some say "terraced tops" or "topmost top", and "viewed some hops" is sometimes rendered as "vaulted a hedge"). A profane example is "Some Anatomists Like F**king, Others Prefer S & M" for the external carotid artery branches. Medical mnemonics are quite common, see . Visual mnemonics are also popular in medicine as well as other fields. In this technique, an image portrays characters or objects whose name sounds like the item that has to be memorized. This object then interacts with other similarly portrayed objects that in turn represent associated information. For example a drug name "hydralazine" could be represented as "lazy hydra" that is on strike holding a sign "NO more work". "NO" in the above case symbolizes Nitric Oxide, which is related to the drug's mechanism of action. For examples of this technique, see .
A way of remembering biological groupings in taxonomy is the phrase "Kings Play Cards On Fat Green Stools", "Kings Play Chess On Fine Grained Sand", "Kings Play Chess Often For Great Sport", and also "Kings Play Chess On Funny Green Squares". Another mnemonic for this purpose is "Kids Prefer Cheese Over Fried Green Spinach". Yet another is "King Phillip Came Over For Good Spaghetti". King Phillip Came Over From Germany, Swimming" is popular in America. "King Penguins Copulate Often For Greater Satisfaction" also works, as does Kevin Please Come Over For Gay Sex, as was popularized on the program TV Funhouse.
Many people remember the Order of Operation in Maths with the word Brackets Of (fractions: 1/2 of 2) Division Multiplication Addition Subtraction (BODMAS or BOMDAS).
Many young Australian children remember the compass points in order in clockwise with the phrase Never Eat Soggy Weetbix (North, East, South, West). Weetbix is a popular breakfast cereal in Australia. Another variation is Never Ever Smoke Weed.
Many secondary school students remember the basic trigonometric functions with the phrase SOH-CAH-TOA (pronounced "soak a toe-uh").
SOH ... Sine = Opposite leg divided by the Hypotenuse
CAH ... Cosine = Adjacent leg divided by the Hypotenuse
TOA ... Tangent = Opposite leg divided by the Adjacent leg
Or, as popularized at Cincinnati'sSt. Xavier High School, they use the simple phrase Sally Can Tell : Oscar Has AHard On Always. (It's been theorized that mnemonic devices that reference strong emotions, such as sexual feelings, imprint a stronger memory. However "Hat On" works equally well, but seems to be less memorable.)
Oscar Had AHeap Of Apples also works if you can remember the sine, cosine, tangent order.
"One Hopes, And Hopes, On America" was widely taught to British schoolchildren during World War II (the sine-cosine-tangent order was presumed). Not only was it a good mnemonic, it also served to reassure the children that Great Britain was not doomed to Nazi annihilation.
You can also remember the basic trigonometric functions with the phrase "Some Old Hippie, Caught Another Old hippie, Tripping On Acid"
Many biology students use the tune of "Row row row your boat" to assist in remembering the characteristics of DNA:
Beginning music students trying to memorize the notes of the staff use the mnemonics "Every Good Boy Does Fine" (or, in Britain, "Every Good Boy Deserves Favour" (also the title of a play with music by Tom Stoppard and Andre Previn), and "FACE" for the lines and spaces of the Treble Clef respectively. The Bass Clef equivalents are "Good Boys Do Fine Always" and "All Cows Eat Grass".
Note: This method of "remembering" note positions on treble and bass clefs will lead to problems later on in music study. It is much better to learn the note positions on the grand staff as a whole and regard the treble and bass clefs as markers.
The acronym HOMES is also a mnemonic aid that can be used to remember the names of the North American Great Lakes (Huron, Ontario, Michigan, Erie, Superior). SHMOE is also useful to remember their positions from North to South, "Super Man Helps Every One" to remember their positions from West to East, and if you like, "Sam's Horse Must Eat Oats" helps one to remember their ordering by size from largest to smallest. (See if you can find others!)
"DOC" represents phases of the Moon by shape: "D" is the waxing moon; "O" the full moon; and "C" the waning moon. In the Southern hemisphere, this is reversed, and the mnemonic is "COD". A French mnemonic is that the waxing moon at its first "premier" quarter phase looks like a 'p', and the waning moon at its last "dernier" quarter looks like a 'd'. In German, the Moon is compared to a handwritten small letter a for "Abnehmen" (waning) and a z for "Zunehmen" (waxing). One more (Northern hemisphere) mnemonic, which works for most Romance languages, says that the Moon is a liar: it spells "C", as in crescere (Italian for "to grow") when it wanes, and "D" as in decrescere ("decrease") when it waxes.
A mnemonic for remembering the number of days in the months of the year, practically a cultural universal in the United States, is "Thirty days hath September/April, June and November." (Although this is only part of a longer rhyme, this is the only part that most people remember, so they commonly complete it with words similar to "... except February, which has twenty-eight, or twenty-nine in a leap year." The full mnemonic is "Thirty days hath September/April, June and November/All the rest have thirty-one/except February alone/which has eight and a score/until leap year gives it one day more.")
Another mnemonic for the days of the months is not a rhyme or a jingle, but a gestalt. Whereas the traditional mnemonic simply associates the name of the month with the number of days, this one emphasizes the sequence. The 31 and less-than-31-day months would be easy to remember if they simply alternated, but the pattern of month lengths is not that simple. They alternate until the fourth 31-day month, July, which is immediately followed by another 31-day month. Since the human hand has four fingers, one can, given an appropriate mind-set, perceive this pattern in a view of the knuckles of two fists, held together. The raised knuckles can be seen as the 31-day months, the dips between them as the 30-day-months-and-February, and the gap between the hands ignored. (Thus: left-hand-pinky-knuckle = January, dip = February, left-hand-ring-knuckle = March, dip = April, and so on to left-hand-index-knuckle = July; then continue with right-hand-index-knuckle = August, dip = September, etc).
Let's not forget the word that reminds us that the best plan is usually a simple plan: K-I-S-S (Keep it Simple, Stupid!)
A curious characteristic of many memory systems is that mnemonic devices work despite being (or possibly because of being) illogical, arbitrary, and artistically flawed. "Roy" is a legitimate first name, but there is no actual surname "Biv" and of course the middle initial "G" is arbitrary. Why is "Roy G. Biv" easy to remember? Medical students never forget the arbitrary nationalities of the Finn and German. Any two of the three months ending in -ember would fit just as euphoniously as September and November in "Thirty days hath...", yet most people can remember the rhyme correctly for a lifetime after having heard it once, and are never troubled by doubts as to which two of the -ember months have thirty days. A bizarre arbitrary association may stick in the mind better than a logical one.
A mnemonic technique is one of many memory aids that is used to create associations among facts that make it easier to remember these facts. Popular mnemonic techniques include mind mapping and peg lists. These techniques make use of the power of the visual cortex to simplify the complexity of memories. Thus simpler memories can be stored more efficiently. For example, a number can be remembered as a picture. This makes it easier to retrieve it from memory. Mnemonic techniques should be used in conjunction with active recall to actually be beneficial. For example, it is not enough to look at a mind map; one needs to actively reconstruct it in one's memory.
Other methods for remembering arbitrary numbers or number sequences use numerological (lit. number+word) systems such as the abjad, where each numeral is represented by a consonant sound. These systems take advantage of the memory's ability to store more information by organizing it into "chunks".
An example of a widely used system for memorizing numbers as words is the major system.
Number rhyme system
This is an example of a "peg list". It is useful for remembering ordered lists, especially for people with strong auditory learning styles. The following numbered list is static. Note the rhyme of the digit and the word (one/bun, two/glue, and so on). The items you wish to remember should be associated with each word. A similar system utilizing a combination of this and the preceding "abjad" system can easily yield numbers through 100 or higher (ex. 76 lash, 77 lilly)
Egg and spear or number shape system
This is another peg system, much like the number-rhyme system but more suitable for those with visual learning styles (a one looks like a candle; a two looks like a swan, and so on).
The "Method of Loci" or Ars memoriae (art of memory) practised in the Classical, Medieval, and Renaissance periods relied on the capacity of the brain for recalling spatial detail. The principle was to initially memorise some large building, the more architectural elaboration of rooms, passages and niches it had the better — the so-called 'Memory Palace'. Mnemonic images could be placed about this palace to link to items that you wanted to remember, usually in symbolic form, with the images as striking as possible to enable recollection. To recall something, the practitioner mentally moved around the palace, reviewing the images in order. This was an essential technique of rhetoricians and preachers.
A reference to this technique survives to this day in the common English phrases "in the first place", "in the second place", and so forth.