An ambigram, also sometimes known as an inversion or flipscript, is a graphical figure that spells out a word not only in its form as presented, but also in another direction or orientation. The text can also consist of a few words, and the text spelled out in the other direction or orientation is often the same, but can also be a different text. Douglas R. Hofstadter describes an ambigram as a "calligraphic design that manages to squeeze two different readings into the selfsame set of curves." The term "ambigram" was first used to mean "ambiguous anagram" by Judith E. Bagai, a former editor of The Enigma, the official organ of The National Puzzlers' League.
According to practitioner John Langdon, ambigrams were independently invented by himself and by Scott Kim in the 1970s. Kim used the name Inversions as the title of his first collection in 1981. The first published reference to "ambigram" was by Hofstadter, who attributes the origin of the word to conversations among a small group of friends during 1983–1984. The 1999 edition of Hofstadter's Gödel, Escher, Bach features a 3-D ambigram on the cover.
Ambigrams became much more popular as a result of Dan Brown incorporating them into the plot of his bestseller, Angels & Demons; Langdon produced ambigrams that were used for the book cover, and a link to his website from Brown's meant he was "suddenly inundated" with commissions. In fact the name Robert Langdon (the hero from the novel) is also an appreciation to Mr. John Langdon.
Ambigrams usually fall into one of several categories:Rotational : A design that presents several instances of words when rotated through a fixed angle. This is usually 180 degrees, but rotational ambigrams of other angles exist, for example 90 or 45 degrees. The word spelled out from the alternative direction(s) is often the same, but may be a different word to the initially presented form. A simple example is the lower-case abbreviation for "Down", dn, which looks like the lower-case word up when rotated 180 degrees.Mirror : A design that can be read when reflected in a mirror, usually as the same word or phrase both ways. Ambigrams that form different words when viewed in the mirror are also known as glass door ambigrams, because they can be printed on a glass door to be read differently when entering or exiting.Figure-ground : A design in which the spaces between the letters of one word form another word.Chain : A design where a word (or sometimes words) are interlinked, forming a repeating chain. Letters are usually overlapped meaning that a word will start partway through another word. Sometimes chain ambigrams are presented in the form of a circle.Space-filling : Similar to chain ambigrams, but tile to fill the 2-dimensional plane.Fractal : A version of space-filling ambigrams where the tiled word branches from itself and then shrinks in a self-similar manner, forming a fractal. See Scott Kim's fractal of the word TREE for an animated example.3-dimensional : A design where an object is presented that will appear to read several letters or words when viewed from different angles. Such designs can be generated using constructive solid geometry.Perceptual shift : A design with no symmetry but can be read as two different words depending on how the curves of the letters are interpreted.Natural : A natural ambigram is a word that possesses one or more of the above symmetries when written in its natural state, requiring no typographic styling. For example, the words "dollop" and "suns" are natural rotational ambigrams. The word "bud" forms a natural mirror ambigram when reflected over a vertical axis. The words "CHOICE" and "OXIDE", in all capitals, form a natural mirror ambigram when reflected over a horizontal axis. The word "TOOTH", in all capitals, forms a natural mirror ambigram when its letters are stacked vertically and reflected over a vertical axis.Symbiotogram : An Ambigram that, when rotated 180 degrees, can be read as a different word to the original.
Graphic artists use ambigrams because of their unique symmetry. Ambigrams thus appear in commercial logos, covers of books and music albums, and tattoo designs.
Ambigrams feature prominently in Dan Brown's novel, Angels and Demons, of which the first UK release featured an ambigram of the title on the cover. The ambigrams in the novel were designed by graphic artist John Langdon. Since the release of the bestseller sequel The Da Vinci Code, there has been a marked increase in the popularity and awareness of ambigrams, leading to a reprint of John Langdon's book on ambigrams entitled Wordplay.
Another example appears in the short story Emma Zunz by Jorge Luis Borges. In this case, the surname of the eponymous main character can be read the same way right side up and upside down.
The comicbook New X-Men used ambigram logo, featuring the name of the title.
The following ambigram examples all have rotational symmetry, unless otherwise noted.