Palindrome

For further examples see Palindromic words and Palindromic phrases: For the movie, see Palindromes (film)

A palindrome is a word, phrase, number or other sequence of units (such as a strand of DNA) that has the property of reading the same in either direction (the adjustment of punctuation and spaces between words is generally permitted). The word "palindrome" was coined from Greek roots Greek πάλιν (palin) "back" and δρóμος (dromos) "way, direction" by English writer Ben Jonson in the 1600s. Composing literature in palindromes is an example of constrained writing.

History

Palindromes date back at least to 79 A.D., as the palindromic Latin word square "Sator Arepo Tenet Opera Rotas" was found as a graffito at Pompeii, buried by ash in that year. This palindrome is remarkable for the fact that it also reproduces itself if one forms a word from the first letters, then the second letters and so forth. Hence it can be arranged into a word square that reads in four different ways: horizontally or vertically from top left to bottom right; and horizontally or vertically from bottom right to top left.

  S A T O R
  A R E P O
  T E N E T
  O P E R A
  R O T A S

While some sources translate this as "The sower Arepo holds the wheels at work", translation is problematic as the word arepo is otherwise unknown; the square may have been a coded Christian signifier, with TENET forming a cross. For further discussion, see separate article.

A palindrome with the same property is the Hebrew palindrome "פרשנו רעבתן שב�"בש נתבער ונשרף", ("parashnu ra'avtan shebadvash nitba'er venisraf"), meaning "We explained the glutton who is in the honey was burned and incinerated", by Ibn Ezra, referring to the halachic question as to whether a fly landing in honey makes the honey non-kosher.

פ ר ש נ ור ע ב ת ןש ב �" ב שנ ת ב ע רו נ ש ר ף

Another Latin palindrome, "In girum imus nocte et consumimur igni" ("We enter the circle at night and are consumed by fire"), was said to describe the behavior of moths. It is likely from medieval rather than ancient times.

Byzantine Greeks often inscribed the palindrome "ΝΙΨΟΝΑΝΟΜΗΜΑΤΑΜΗΜΟΝΑΝΟΨΙΝ" on baptismal fonts; in mixed case with modern accents and divided into words this reads "Νίψον ανομήματα μη μόναν όψιν" ("Nipson anom�"mata m�" monan opsin"), meaning "Wash the sins, not face alone" (ps, ψ, is the single Greek letter psi).

Palindromes in languages with different writing systems

In languages that use a writing system other than an alphabet, a palindrome is still a sequence of characters from that writing system that remains the same when reversed.

Japanese palindromes, called kaibun, rely on the hiragana syllabary. An example is the word し�"ぶ�"し shinbunshi (in syllables shi-n-bu-n-shi), meaning "newspaper". The Japanese syllabary makes it possible to construct very long palindromes.

A Chinese word is a character, and is not composed of letters or syllables. Therefore, a Chinese word itself cannot be a palindrome. Chinese palindromes have to be phrases or sentences and are much more easy to construct than in languages written with an alphabet. For example, the phrases "我愛媽媽，媽媽愛我" ("I love mother, mother loves me") and "上海自來水來自海上" ("Shanghai's tap water comes from the sea") are palindromes. Palindromic poetry" (回文詩) was a literary genre in classical Chinese literature. The "forward reading" and the "backward reading" of such a poem would be similar but not exactly the same in meaning. The following palindromic poem was composed during the Song Dynasty:

枯眼望遙山�"水，往來曾見幾心知。壺空怕酌一杯�'，筆下難成�'�韻詩。迷路阻人離別久，訊音無雁寄回遲。孤燈夜守長寥寂，夫憶妻兮父憶�'。

The "forward reading" of the last sentence is about husband missing wife and father missing son, while the "backward reading" is about son missing father and wife missing husband.

Types of palindrome

:Examples of palindromes are listed at Palindromic words and Palindromic phrases.

Symmetry by characters

The most familiar palindromes, in English at least, are character-by-character: the written characters read the same backwards as forwards. Palindromes may consist of a single word (such as "civic"), a phrase or sentence ("Was it a cat I saw?"), or a longer passage of text. Spaces, punctuation and case are usually ignored.

Three famous English palindromes are: "Able was I ere I saw Elba," honoring the first exile of Napoleon, "A man, a plan, a canal. Panama," commemorating Theodore Roosevelt, and "Madam, in Eden I'm Adam," generally said to refer to the beginning of man in the Bible. (This last example is still palindromic if "in Eden" is omitted.)

Another example common amongst children is "Rats live on no evil star"

Symmetry by words

Some palindromes use words as units rather than letters. An example is "fall leaves after leaves fall" or "First Ladies rule the State and state the rule: ladies first".

Symmetry by lines

Still other palindromes take the line as the unit. The poem Doppelganger, composed by James A. Lindon, is an example.

The dialogue "Crab Canon" in Douglas Hofstadter's Gödel, Escher, Bach is nearly a line-by-line palindrome. The second half of the dialog consists, with some very minor changes, of the same lines as the first half, but in reverse order and spoken by the opposite characters (i.e., lines spoken by Achilles in the first half are spoken by the Tortoise in the second, and vice versa). In the middle is a non-symmetrical line spoken by the Crab, who enters and spouts some nonsense, apparently triggering the reversal. The structure is modeled after the musical form known as crab canon, in particular the canon a 2 cancrizans of Johann Sebastian Bach's The Musical Offering.

Symmetry by sound

Some palindromes are by sound, such as the Hungarian A bátya gatyába ("The brother in underpants"), or the Japanese Ta-ke-ya-bu ya-ke-ta (竹薮焼けた) ("A bamboo grove has been burned").

Acoustic symmetry

The only known palindrome in which a recorded phrase of speech sounds the same when it is played backwards was discovered by the composer John Oswald in 1974 while he was working on audio tape versions of the cut-up technique using recorded readings by William S. Burroughs. Oswald discovered that in repeated instances of Burroughs speaking the phrase "I got", that the recordings sound nearly identical when played backwards or frontwards.

Numbers

See main article: Palindromic number

Dates and times

Palindromes can also be constructed using dates and times. The exact dates and times may differ according to the local style (for example, whether the month or day is written first). For example:
12/02/2021 for February 12th, 2021, using the DD/MM/YYYY format.
10/30/2002 03:01 for October 30th, 2002, 3:01 AM, using the MM/DD/YYYY HH:MM format.
10/3/01 for October 3rd, 2001, using the MM/DD/YY format (0 as a place holder, not shown).

Palindrome Years happen once a century.

In music

The light music composer Ronald Binge was interested in musical palindromes. he composed a piano piece known as Vice Versa, innovative in that it was not only a front-to-back palindrome as read, but exploited the two staves used for writing for piano and was the first pice to also work in an up-and-down manner (that is, the music reads the same whatever way it is turned or even if it is read in a mirror). He later extended this theme, composing a remarkable piece known as Upside/Downside for his son, who was learning recorder at Downside School. This musical palindrome was for piano, recorder and cello and again was universally reversible - two players could therefore play from the same sheet of music reading from opposite ends and in opposite directions!

Nerdcore rapper MC Paul Barman, in his song Bleeding Brain Grow from the album Paullelujah, raps several lines written in palindrome, mostly name-dropping some of his favorite rappers:
"Eve,
Mika, RZA, Evil JD, Nasir is Osiris, and J. Live, AZ, Rakim,
Cormega, Cage, Mr. O.C.,
I'm Anomi. I, mon ami!"

On his 2003 album Poodle Hat, the comedy singer "Weird Al" Yankovic included a song called Bob composed entirely of rhyming palindromes. The name Bob is itself a palindrome, and is also a reference to Bob Dylan, whose Subterranean Homesick Blues he emulated in both the song's style and the accompanying video.

The title of Aoxomoxoa (pronounced "OX-OH-MOX-OH-AH") by the Grateful Dead is a palindrome.

The singer and guitarist Baby Gramps wrote and performs a song entitled Palindromes.

Boards of Canada's song "A is to B as B is to C" contains an audio palindrome.

The musical duo of John Linnell and John Flansburgh, also known as They Might be Giants, wrote a song related to palindromes called I Palindrome I. The song appears on their album Apollo 18. At one point in the song, the lyrics are the same forwards as backwards: "Son, I am able she said though you scare me, watch, said I, beloved, I said watch me scare you though, said she able am I, son." They also include the palindromic phrase: "Egad a base tone denotes a bad age." and also the palindromic word, "manonam".

The Icelandic band Sigur Rós composed a song on their album Ágætis byrjun which partly sounds the same played forwards or backwards. The notes have a symmetric form, and a reversed version of the music is mixed over the original. The song—named Starálfur—can be downloaded from their website.

The singer-songwriter-violinist Andrew Bird wrote and performs a song entitled Fake Palindromes. It is performed on the album Andrew Bird & the Mysterious Production of Eggs.

The interlude from Alban Berg's opera Lulu is a palindrome, as are sections and pieces, in arch form, by many other composers, including James Tenney (swell), and most famously Béla Bartók (and, influenced by him, Steve Reich).

Every song on Michael Perilstein's album Godzilla vs. Your Mother has a palindromic title.

In 1992, the band Soundgarden released an EP entitled Satanoscillatemymetallicsonatas, or SOMMS for short. The title itself is a palindrome.

In Finland, Tapani Länsiö composed a choral work which is a palindrome both musically, and lyrically, Atte kumiorava, varo imuketta (Atte the rubber-squirrel, do beware the cigar-holder).

See also crab canon — in classical music, a canon in which one line of the melody is reversed in time and pitch from the other.

In fiction

The "Fault Lines" trilogy of novels written by author Tim Powers refer to palindromes regularly as means of capturing or otherwise trapping ghosts and other supernatural entities. The claim made in the books is that palindromes, being cyclical in nature (reading forward, then backward, then forward again, ad infinitum) cause these 'idiot' ghosts to become enamored, hypnotized by the constant reading and re-reading. Initially this concept is introduced as a way to explain that ghosts can be so trapped or attracted to a place if so-desired by someone wanting to communicate or exploit the weakness of the dead. Most commonly used in the last novel, Earthquake Weather, are three Latin palindromes:

Si bene te tua laus taxat, sua laute tenebis.
Roma tibi subito motibus ibit amor.
Sole medere, pede ede, perede melos.

In the novel Holes by Louis Sachar (which has been made into a film by Walt Disney Pictures), the main character is named Stanley Yelnats, as are his father and grandfather.

A character in Bruce Sterling's Zeitgeist speaks exclusively in palindromes.

Computer programs

Brian Westley wrote a C program for the 1987 International Obfuscated C Code Contest which is a line-by-line palindrome: http://www.ioccc.org/1987/westley.c

Up to the type definitions, here is a compilable palindrome written in Caml:

type 'a elbatum = 'a ;;

 type lol = bool ;;
 type pop = int ;;
 type b = { mutable lol : lol elbatum } ;;

type i = { mutable pop : pop elbatum } ;;

fun erongi lol pop n -> pop.lol <- let nuf = erongi ; fun erongi lol pop n -> pop.lol ; ignore

 n in

erongi ; lol.pop <- n pop lol ignore nuf ; ignore = fun tel -> lol.pop <- n pop lol ignore nuf;

Long palindromes

The longest palindromic word in the Oxford English Dictionary is tattarrattat, coined by James Joyce in Ulysses for a knock on the door. The Guinness Book of Records gives detartrated, the past tense of detartrate, a somewhat contrived chemical term meaning to remove tartrates. Rotavator, a trademarked name for an agricultural machine, is often listed in dictionaries. The term redivider (i.e. someone or something that redivides) is used by some writers but appears to be an invented term - only redivide and redivision appear in the "Shorter Oxford Dictionary". Malayalam, an Indian language, is of equal length.

Saippuakauppias, Finnish for "soap vendor", is claimed to be the world's longest palindromic word in everyday use. A meaningful derivative from it is saippuakalasalakauppias (soapfish bootlegger). An even longer effort is saippuakuppinippukauppias (soapdish batch seller) Koortsmeetsysteemstrook, is probably the longest palindrome in Dutch, and Kuulilennutunneliluuk (trajectory tunnel hatch) is the longest palindrome in Estonian.

To celebrate 20:02 02/20 2002, a palindromic day, Peter Norvig wrote on that day a computer program which produced the world's longest palindromic sentence, running to 17,259 words [1].

A long palindrome in English that reads more easily and attempts to flow is reproduced here.

In 1991, Gordon Dow composed a 306 word palindrome titled Dog Sees Ada. This palindrome is famous for using very few contrived words. It is reproduced here.

The poet Graywyvern wrote a 427-line palindromic poem, "The Angel of Death," in 2005, still available both online and in hard copy.

Two "palindromic novels" appeared, in limited editions, during the 1980s: Dr Awkward & Olson in Oslo by Lawrence Levine (self-published, St Augustine FL); and Satire: Veritas by David Stephens (Word Ways Monographs) (references).

Longest palindromes in Polish

Stanisław Barańczak, a Polish poet and translator created a Mega-Palindromader which is based on symmetry by letters. This work in Polish is composed of 4 introductory small palindromes (as the author called them, 'fanfares') and the main 2,501-letter palindrome. This was bettered by Prof. Tadeusz Morawski, Polish palindrome enthusiast and author, who published two longer palindromes in his 2005 book Gór ech chce róg. In June 2006, Prof. Morawski announced he has created a record-breaking 33,000-letter palindrome, published on his webpage [2], gaining some coverage in national press.

Biological structures

In most genomes or sets of genetic instructions, palindromic motifs are found. However, the meaning of palindrome in the context of genetics is slightly different to the definition used for words and sentences. Since the DNA is formed by two paired strands of nucleotides, and the nucleotides always pair in the same way (Adenine (A) with Thymine (T), Cytosine (C) with Guanine (G)), a (single-stranded) sequence of DNA is said to be a palindrome if it is equal to its complementary sequence read backwards. For example, the sequence ACCTAGGT is palindromic because its complement is TGGATCCA, which is equal to the original sequence in reverse.

A palindromic DNA sequence can form a hairpin. Palindromic motifs are made by the order of the nucleotides that specify the complex chemicals (proteins) which, as a result of those genetic instructions, the cell is to produce. They have been specially researched in bacterial chromosomes and in the so-called Bacterial Interspersed Mosaic Elements (BIMEs) scattered over them. Recently a research genome sequencing project discovered that many of the bases on the Y chromosome are arranged as palindromes. A palindrome structure allows the Y chromosome to repair itself by bending over at the middle if one side is damaged.

Computation theory

In automata theory, a set of all palindromes in a given alphabet is a typical example of a language which is context-free, but not regular. It is also an example of a context-free language which cannot be accepted by a deterministic pushdown automaton.[3]

Further examples

For numerous further examples of palindromes in a variety of different languages see Palindromic words and Palindromic phrases.

Poking fun at palindromes

In their famous Dead Parrot sketch Monty Python poke fun at palindromes:

Shopkeeper(Michael Palin): I said Bolton -it was supposed to be a pun, no, the thing spelled the same backwards and forwards - it was a palindrome.

Customer(John Cleese): A palindrome?! The palindrome of Bolton would be Notlob - it don't work!

The palindrome in Greek

Even though the word Palindrome was constructed from Greek roots, the Greek expression to describe a Palindrome is "Καρκινική επιγραφή" (literally translated: "Crab inscription"), or simply "Καρκινιήοι" (crabs) from the backward movement of crabs - therefore, an inscription which can be read backwards).

See also

* ambigram
* anagram
* backward message
* crab canon
* holorhyme
* pangram
* palindromic number
* transcription (linguistics)
* word games
* word play

External links

*Zo's Palindrome Mosaic
*Palindrome of the Day
*Palindromes - in Polish.
*Palindromes
*Palíndromos - In Portuguese.
*Palindromes Quiz
*Jason Doucette - 196 Palindrome Quest / Most Delayed Palindromic Number
*An alphabetized collection of palindromes
*Palindrome Also-Rans - The palindromes that didn't quite make it
* http://abitheone.blogspot.com/2005/07/palindromic-pal.html (Humor using palindromes)
*Dictionary of Current English Palindromes
*Short repeated palindromes in enterobacteria
*A Palindrome: Conscious Living Creatures as Instruments of Nature; Nature as an Instrument of Conscious Living Creatures
*A 'Mega-Palindromadery' by Polish poet, Stanisław Barańczak
*196 and Other Lychrel Numbers that do NOT become palindromes
*Oswald's audio cut-ups of William S. Burroughs including an acoustic palindrome in example 5

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