The crossword is the most common variety of word puzzle in the world. Modern crosswords normally take the form of a square grid of black and white squares; the aim is to fill the white squares with letters, forming words (or word phrases) reading across and down, by solving clues which yield the words. The black squares are used to separate words. Squares in which answers begin are usually numbered; the clues are then referred to by these numbers and a direction – for example, "1-Across" or "17-Down"; at the end of the clue the total number of letters is sometimes given for the convenience of the solver, dependent on the style of puzzle and country of publication.

Terminology

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The creating of crosswords is called 'cruciverbalism' among its practitioners, who are likewise referred to as 'cruciverbalists'; the terms derive from the Latin for 'cross' and 'word'. Although the terms have existed for over a decade, non-cruciverbalists rarely use them, calling crossword creators simply 'constructors' or 'setters'.

The horizontal and vertical lines of white cells into which answers are written are commonly called 'entries' or simply 'answers'; the clues themselves are usually called just that, or sometimes 'definitions'. The black and white cells themselves have several terms, such as "darks and lights", "blanks" (which refers to the black cells, which are left unfilled by solvers and serve as spacers), and the like.

A white cell that is part of only one entry - Across or Down, but not both - is usually called 'unchecked'; 'unkeyed' or just 'uncrossed' are other names for this.

Types of grid

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Crossword grids such as those appearing in most North American newspapers and magazines feature solid chunks of white squares. Every letter is checked (that is, it is part of an answer reading across and another reading down), and usually each answer is required to contain at least three letters. In such puzzles black squares, used to separate answers, are traditionally limited to about one-sixth of the design. Crossword grids elsewhere, such as in Britain and Australia, have a lattice-like structure, with a higher percentage of black squares, leaving up to half the letters in an answer unchecked. In these puzzles it is normally the case that no two across or down answers may run side-by-side. For example, if the top row has an answer running all the way across, there will be no across answers in the second row.

Another tradition in puzzle design (in North America and Britain particularly) is that the grid should have 180-degree rotational symmetry, so that its pattern appears the same if the paper is turned upside down. Puzzles are often one of several standard sizes. For example, many weekday puzzles (such as the New York Times crossword) are 15×15 squares, while weekend puzzles may be 21×21, 23×23 or 25×25.

The design of Japanese crossword grids often follows three additional rules: that black cells may not share a side, that all white cells must be orthogonally contiguous (that is, connected in one mass through shared sides, or form a single polyomino), and that the corner squares must be white.

Substantial variants from the usual forms exist. Two of the common ones are barred crosswords which use bold lines between squares (instead of black squares) to separate answers, and circular designs, with answers to be entered either radially or in concentric circles. Free form crosswords have simple designs and are not symmetric.

Typically, clues appear outside the grid, divided into an Across list and a Down list; correspondingly, the first cell of each entry contains a number referenced by the clue lists - for example, the answer to a clue labeled "17-Down" would be entered with the first letter in the cell numbered '17' and proceed down from there. Numbers are almost never repeated; instead, all cells that require clue numbers are labeled consecutively, usually from left to right across each row, starting with the top row and proceeding downward (some Japanese crosswords are numbered from top to bottom down each column, starting with the leftmost column and proceeding right).

German and Brazilian crosswords usually don't number the clues; instead, the clues themselves are found in small print inside the grid cells, each clue with a little arrow indicating in which direction from its cell the answer is to be written. These "clue boxes" are usually the only (or nearly so) "black squares" in such puzzles. This is not uncommon in other languages as well (English examples are regularly published in GAMES Magazine under the title Pencil Pointers).

Answers are printed in upper case letters. This ensures a proper name can have its initial capital letter checked with a non-capitalizable letter in the intersecting clue. Diacritical markings in foreign loanwords are ignored for similar reasons. This also applies in foreign-language puzzles; for example, in French, the initial Ê of answer ÊTRE can double as the final É of CONGÉ when written ETRE and CONGE. In German language crosswords, the umlauts 'ä', 'ö', and 'ü' are dissolved into 'ae', 'oe', and 'ue', and ß is dissolved into ss.

Types of clues

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Straight or quick

In some crosswords, often called straight or quick, the clues are usually simple definitions for the answers. Some clues may feature anagrams, but these are usually explicitly described as such. Often, a straight clue is not in itself sufficient to distinguish among several possible answers (often synonyms), and the solver must make use of checks to establish the correct answer with certainty. A key point to remember when solving crosswords is that crossword answers and their clues always agree in tense and number. If a clue is in the past tense, then so is the answer: "Traveled on horseback" = RODE, but never RIDE. Similarly, "Family members" would be a valid clue for AUNTS but not UNCLE (since the latter is singular while the clue is plural). Some clue examples:

• Fill-in-the-blank clues are often the easiest in a given puzzle, and a good place to start solving. Ex.: "__ Boleyn" = ANNE
• Abbreviations, use of foreign language, variant spellings, or other unusual word tricks are indicated in the clue. A crossword creator might choose to clue the answer SEN (as in the abbreviation for "Senator") as "Washington bigwig: Abbr." or "Member of Cong.", with the abbreviation in the clue indicating that the answer is to be similarly abbreviated. The use of "Var." indicates the answer is a variant spelling (e.g., EMEER instead of EMIR), while the use of foreign language or a foreign place name within the clue indicates that the answer is also in a foreign language. For example, ETE (French for "summer") might be clued as "Summer, in the Sorbonne" while ROMA could be clued as "Italia's capital."
• A question mark at the end of clue usually signals that the clue/answer combination involves some sort of pun. Ex.: "Grateful?" = ASHES (since a grate might be full of them).
• The clue "PC key" for a three-letter answer could be ESC, ALT, TAB, or even DEL, but until a check is filled in, giving at least one of the letters, the correct answer cannot be determined.
• A common clue is "Compass point", where the desired answer is one of eight possible abbreviations for a position on a compass, i.e. NNW (for north-northwest) or ESE (for east-southeast). The desired answer is determined by a combination of logic - since the third letter can be only E or W, and the second letter can be only N or S - and a process of elimination using checks. Alternatively, compass point answers are often clued as "XXX to YYY direction", where XXX and YYY are two place names. For example, SSW might be clued as "New York to Washington direction".
• Most widely distributed American crosswords today (e.g., The New York Times, Washington Post, Boston Globe, USA Today, etc.) also contain "speech"-like answers, i.e., entries in the puzzle grid that try to replicate our everyday colloquial language. In such a puzzle, one might see phrases such as WHAT'S UP, AS IF, or WHADDYA WANT.

The British-style cryptic crossword crossword is laden with wordplay, and features a very different type of clue from those listed above. For more details see the dedicated section, below.

Crossword themes

Many American crossword puzzles contain a "theme," consisting of a number of long entries (generally 3-5 in a standard 15x15-square "weekday"-size puzzle) that share some relationship, type of pun, or other element in common. As an example, the New York Times crossword of April 26, 2005 written by Sarah Keller and edited by Will Shortz, featured five theme entries ending in the different parts of a tree:

SQUAREROOT

TABLELEAF

WARDROBETRUNK

BRAINSTEM

BANKBRANCH

The above is an example of a category theme, where the theme elements are all members of the same set. Other types of themes include quote themes, featuring a famous quote broken up into parts to fit in the grid (and usually clued as "Quote, part 1", "Quote, part 2", etc.); rebus themes, where multiple letters or even symbols occupy a single square in the puzzle (e.g., BERMUDAΔ); pun-based themes (perhaps the most common), where all the answers are similar puns; commemorative themes, based on a particular event or person (often published on an appropriate anniversary); and other less common types.

The Simon & Schuster Crossword Puzzle Series has published many unusual themed crosswords. "Rosetta Stone," by Sam Bellotto Jr., incorporated a Caesar Cipher cryptogram as the theme; the key to breaking the cipher was the answer to 1 Across. Another unusual theme required the solver to use the answer to a clue as another clue. The answer to that clue was the real solution.

Common Clues

Some words generally accepted as appearing commonly in crossword puzzles include:

• Aida - the opera masterpiece of Giuseppe Verdi
• Alda - star of M*A*S*H
• Aloe - ingredient used in lotions, moisturizers
• Alto - high range of voice, instrument
• Aria - the solo in an opera
• Emir - Middle East ruler
• Et al. - list ender
• E. Lee - Gen. Robert _______
• Esai - actor ____ Morales
• Oleo - butter substitute
• Stet - to reverse a correction in the proofreading process, to leave in

Quiz crosswords

In quiz crosswords, the clues take the form of questions. These may be on general knowledge or on a single topic.

The first entries

In the Daily Telegraph newspaper (Sunday and Daily, UK), it has become a convention also to make the first few words (usually 2 or 3 but can be up to 5) into a phrase. For example, "Dimmer, Allies" would make "Demoralise" or "You, ill, never, walk, alone" would become "You will never walk alone". This generally aids the solver in that if they have one of the words then they can attempt to guess the phrase. This has also become popular among other British newspapers.

Indirect clues

In many puzzles, some clues are to be taken metaphorically or in some sense other than their literal meaning. Depending on the puzzle creator or the editor, this might be represented either with a question mark at the end of the clue or with a modifier such as "maybe" or "perhaps". Examples:

• The clue "Half a dance?" for a 3-letter answer might be CAN (half of CANCAN) or CHA (half of CHACHA).
• The clue "Pay addition, perhaps", without the modifier might be something akin to "BONUS". However, with the modifier, the answer could be "OLA" (the addition of OLA to PAY is the word PAYOLA).

Cryptic crosswords

In cryptic crosswords, often called cryptics for short, the clues are puzzles in themselves. A typical clue contains a definition, located at the beginning or end of the clue, and wordplay, which describes the word indicated by the definition, and which may not parse logically, but should be at least grammatical. Cryptics usually give the length of their answers in parentheses after the clue. In cryptics, answers are given in all capitals, with certain signs indicating different wordplay. Cryptics have a steeper "learning curve" than standard crosswords as learning to interpret the different types of cryptic clues can take some practice. In Great Britain, cryptics are the most common variety of crossword puzzle.

There are several types of wordplay used in cryptics. One is straightforward definition substitution using parts of a word. For example, in one puzzle by Mel Taub, the answer IMPORTANT is given the clue "To bring worker into the country may prove significant". The explanation is that to "import" means "to bring into the country"; the "worker" is a worker ant; and "significant" means "important." Note that in a cryptic clue, there is almost always only one answer that fits both the definition and the wordplay, so that when you see the answer, you know it is the right answer, although it can sometimes be a challenge to figure out why it is the right answer.

A good cryptic clue should exactly explain the answer, while at the same time giving a meaningful surface reading. In our sample clue, a more exact wordplay phrasing would be "To bring into the country a worker may prove significant", since "ant" follows "import:" IMPORT + ANT. Note however, that the surface reading is then not as smooth as the original. Some cryptic clue devotees would also be upset by the extraneous words like may prove.

Another type of wordplay used in cryptics is homophones. For example, the clue "Counts spots aloud (4)" is solved by ADDS. The definition is "Counts", meaning "adds". The solver must guess that "aloud" here indicates a homophone, and so a homophone of a synonym of "spots" is the answer. In this case "spots" means advertisements, or ads, in mainly British usage. ADS = "ADDS".

Another wordplay commonly used is the double meaning. For example, "Cat's tongue (7)" is solved by PERSIAN, since this is a type of cat, as well as a tongue, or language.

Cryptics very often include anagrams. The clue "Ned T.'s seal cooked is rather bland (5,4)" is solved by NEEDS SALT. The meaning is "rather bland", and the word "cooked" is a hint to the solver that this clue is an anagram (the letters have been "cooked", or jumbled up). "Nedtsseal" (ignoring all punctuation, of course) is an anagram for NEEDS SALT. Besides "cooked", other common hints that the clue contains an anagram are words such as "scrambled," "mixed up," "confused," "baked," "twisted," etc. In answer sheets, an anagram is commonly indicated by an asterisk.

Embedded words are another common trick in cryptics. The clue "Bigotry aside, I'd take him (9)" is solved by APARTHEID. The meaning is "bigotry", and the wordplay explains itself, indicated subtly by the word "take" (since one word "takes" another): "aside" means APART and I'd is simply ID, so APART and ID "take" HE (which is, in cryptic crossword usage, a perfectly good synonym for "him"). The answer would be elucidated as: APART(HE)ID.

And then there is the oft-used hidden clue, where the answer is literally hidden in the text of the clue itself. For example, "Made a dug-out, buried, and passed away (4)" is solved by DEAD. The answer is written in the clue: "maDE A Dug-out". The word "buried" is there to indicate to the solver that the answer is literally embedded within the clue somewhere.

Actually, there is no end to the wordplay found in cryptic clues. Backward words can be indicated by words like "climbing", "retreating", or "coming down"; letters can be replaced or removed with indicators such as "nothing rather than excellence" (meaning replace E in a word with O); the letter I can be indicated by "me" or even "one;" the letter O can be indicated by "nought" or even "a ring" (since it visually resembles one); the letter X might be clued as "a cross", or "ten" (as in the Roman numeral), or "an illiterate's signature", or even "sounds like your old flame" (homophone for "ex"); and so forth. Another example is this: "senselessness" is solved by "e", because "e" is what remain after removing (less) "ness" from "sense".

With the different types of wordplay and definition possibilities, the composer of a cryptic puzzle is often presented with many different possible ways to clue a given answer. Most desirable are clues that are clean but deceptive, with a smooth surface reading. The Usenet newsgroup rec.puzzles.crosswords has a number of clueing competitions where contestants all submit clues for the same word and a judge picks the best one.

In principle, each cryptic clue is usually sufficient to uniquely define its answer, so it should be possible to answer each clue without use of the grid. In practice, the use of checks is an important aid to the solver. (Cryptic crosswords are not to be confused with cryptograms, a different form of puzzle based on a substitution cipher.)

Translation crosswords

In Translation Crosswords, the clue is given in a foreign language. This makes them an entertaining vocabulary trainer. An example of Translation Crosswords created by David Andersen, uses headlines from newspapers as a part of the clue. This enables the user to see the word used in a context, while also being introduced to newspapers in the language he/she wants to learn. A more basic kind of Translation Crosswords can be seen on the pages of yourDictionary.

Other puzzles

Any type of puzzle may contain cross-references, where the answer to one clue forms part of another clue, in which it is referred to by number.

When an answer is composed of multiple or hyphenated words, some crosswords (especially in Britain) indicate the structure of the answer, while others do not. For example, "(3,5)" after a clue would indicate that the answer is composed of a three letter word followed by a five letter word.

Double clue lists

Sometimes newspapers publish one grid which can be filled by solving either of two lists of clues - usually a straight and a cryptic. The solutions given by the two lists may be different, in which case the solver must decide at the outset which list they are going to follow, or the solutions may be identical, in which case the straight clues offer additional help for a solver having difficulty with the cryptic clues. For example, the solution APARTHEID might be clued as "Bigotry aside, I'd take him (9)" in the cryptic list, and "Racial separation (9)" in the straight list.

Every issue of GAMES Magazine contains a large crossword with a double clue list, under the title The World's Most Ornery Crossword; both lists are straight and arrive at the same solution, but one list is significantly more challenging than the other. The solver is prompted to fold a page in half, showing the grid and the hard clues; the easy clues are tucked inside the fold, to be referenced if the solver gets stuck.

A variant of the double clue list is commonly called Siamese Twins: two matching grids are provided, and the two clue lists are merged together such that the two clues for each entry are displayed together in random order. Determining which clue is to be applied to which grid is part of the puzzle.

Example

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Here is a small example of a regular crossword, to illustrate the format:

1		2
3				4
		5

Across

1. Sheep sound (3)
3. Neither liquid nor gas (5)
5. Humour (3)

Down

1. Road passenger transport (3)
2. Permit (5)
4. Shortened form of Dorothy (3)

The solution to this crossword is:

1B	9A	2A	.	.
9U	.	9L	.	.
3S	9O	9L	9I	4D
.	.	9O	.	9O
.	.	5W	9I	9T

A set of cryptic clues that provide the same answers as above might be:

Across

1. Start of announcement by British Airways sounds woolly? (3)
3. Real dirty, mixed up and lacking drug (5)
5. Wilde's intelligence (3)

Down

1. Ferry sees submarine rising (3)
2. Now without its initial after every warrant (5)
4. Do time? There's a point (3)

Major crossword variants

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These are common crossword variants which vary more from a regular crossword than just an unusual grid shape or unusual clues; these crossword variants may be based on different solving principles and require a different solving skill set.

Cipher crosswords

Published under various trade names, and not to be confused with cryptic crosswords (which happens due to ciphertext puzzles being commonly known as cryptograms), a cipher crossword replaces the clues for each entry with clues for each white cell of the grid - an integer from 1 to 26 inclusive is printed in the corner of each. The objective, as any other crossword, is to determine the proper letter for each cell; in a cipher crossword, the twenty-six numbers serve as a cipher for those letters: cells that share matching numbers are to be filled with matching letters, and no two numbers stand for the same letter. All resultant entries must be valid words. Usually, at least one number's letter is already given at the outset. Cipher crosswords are always pangrammatic (all letters of the alphabet appear in the solution). As these puzzles are closer to codes than quizzes, they require a different skillset; many basic cryptographic techniques, such as determining likely vowels, are key to solving these. Given their pangrammaticity, a frequent start point is locating where 'Q' and 'U' must appear.

Diagramless crosswords

In a diagramless crossword, often called a diagramless for short or, in the UK, a skeleton crossword or carte blanche, the grid offers overall dimensions, but the locations of most of the clue numbers and black squares are unspecified. A successful solver must deduce not only the answers to individual clues, but how to fit together partially built-up clumps of answers into larger clumps with properly set black squares. Some of these puzzles follow the traditional symmetry rule, others have left-right mirror symmetry, and still others have greater levels of symmetry or outlines suggesting other shapes. If the symmetry of the grid has been given, then the solver can use it to his/her advantage.

A variation is the Blankout puzzle in the Daily Mail Weekend magazine. In this version, the clues are not individually numbered, but given in terms of the rows and columns of the grid, which has rectangular symmetry. The list of clues gives hints of the locations of some of the black squares even before one starts solving them, e.g. there must be a black square where a row having no clues intersects a column having no clues.

Fill-in crosswords

A fill-in crossword (also known as crusadex or cruzadex) features a grid and the full list of words to be entered in that grid, but does not give explicit clues for where each word goes. The challenge is figuring out how to integrate the list of words together within the grid so that all intersections of words are valid. Fill-in crosswords may often have somewhat longer word length than regular crosswords to make the crossword easier for the solver, as fitting together several long words is easier than fitting together several short words because there are fewer possibilities for how the long words intersect together.

Crossnumbers

A crossnumber is the exact numerical analogy of a crossword, in which the solutions to the clues are numbers instead of words. Clues are usually arithmetical expressions, but can also be general knowledge clues to which the answer is a number or year. There are also numerical fill-in crosswords.

The Daily Mail Weekend magazine used to feature crossnumbers under the misnomer Number Word. This kind of puzzle should not be confused with a different puzzle that the Daily Mail refers to as Cross Number.

Crosswords in non-English languages

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Although the crossword is an English-language invention and most common in English-speaking countries, other countries have crosswords in their respective languages.

French-language crosswords are smaller than English-language ones, and not necessarily square: usually 8–13 rows and columns, totalling 81–130 squares. They need not be symmetric and two-letter words are allowed, unlike in most English-language puzzles. Compilers strive to minimize use of black squares. 10% is typical; Georges Perec compiled many 9×9 grids for Le Point with 4 or even 3 ^*. Rather than numbering the individual clues, the rows and columns are numbered as on a chessboard. All clues for a given row or column are listed, against its number, as separate sentences. This is similar to the notation used in the aforementioned Daily Mail Blankout puzzles.

In Italy, crosswords are usually oblong and larger than French ones, 13x21 being a common size. As in France, they usually are not symmetrical; two-letter words are allowed; and the number of black squares is minimized. Nouns (including surnames) and the infinitive or past participle of verbs are allowed, as are abbreviations; in larger crosswords, it is customary to put at the center of the grid phrases made of two to four words, or forenames and surnames. A variant of Italian crosswords does not use black squares: words are delimited by thickening the grid. Another variant starts with a blank grid: the solver must insert both the answers and the black squares. In this case, Across and Down clues are ordered by row and column.

Particularly curious is the Japanese language crossword; due to the writing system of that nation's language, one syllable (typically katakana) is entered into each white cell of the grid rather than one letter, resulting in the typical solving grid seeming rather small in comparison to those of other languages. Even cipher crosswords have a Japanese equivalent, although pangrammaticity does not apply.

In Poland, crosswords can only contain nouns, singular or plural. Other parts of speech are very rare. The crosswords typically use British-style grids, but some don't have black cells at all.

History

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On December 21, 1913, Arthur Wynne published a "word-cross" puzzle in the New York World which embodied most of the features of the genre as we know it. This puzzle, which can be seen at this website, is frequently cited as the first crossword puzzle, and Wynne as the inventor. Later, the name of the puzzle was changed to "crossword." A more complete history of the crossword puzzle, as well as a reprint of that very first crossword, can be found at a page maintained by New York Times crossword editor Will Shortz here.

Crossword puzzles became a regular weekly feature in the World. The first book of crossword puzzles, however, did not appear until 1924, published by Simon and Schuster. The book was an instant hit and crossword puzzles became the craze of 1924. The term crossword first appeared in a dictionary in 1930.

Today, there are many popular crosswords distributed in American newspapers and online. The most prestigious (and among the most difficult to solve) are the New York Times crossword puzzles, which have been running continuously since 1942. The first editor of the Times crossword was Margaret Farrar, who was editor from 1942 to 1969. She was succeeded by Will Weng, who was succeeded by Eugene T. Maleska. Since 1993, they have been edited by Will Shortz, the fourth crossword editor in Times history. In addition to editing the Times puzzles, in 1978 Shortz founded and still directs the annual American Crossword Puzzle Tournament.

Simon and Schuster also continues to publish the Crossword Series books which it began in 1924, currently under the editorship of John M. Samson.

The British cryptic crossword was imported to the US in 1968 by composer and lyricist Stephen Sondheim in New York magazine. Until 2006, the Atlantic Monthly regularly used to feature a cryptic crossword "puzzler" by Emily Cox and Henry Rathvon, which combines cryptic clues with diabolically ingenious variations on the construction of the puzzle itself. In both cases, no two puzzles are alike in construction, and the intent of the puzzle authors is to entertain with novelty, not to establish new variations of the crossword genre.

History in the United Kingdom

In the United Kingdom, the Sunday Express newspaper published the first British crossword on November 2, 1924. Several crossword experts were recruited into code-breaking activities during World War II at Bletchley Park in England.

Crossword puzzles in World War II

In 1944, Allied security officers were disturbed by the appearance, in a series of crossword puzzles published in The Daily Telegraph, of words that happened to be secret code names for military operations. "Utah" (the code name for one of the landing sites) appeared in a puzzle published on May 2, 1944. Subsequent puzzles included the words "Omaha" and "Mulberry" (the highly-secret artificial harbours).

On June 2, just four days before the invasion, the puzzle included both the words "Neptune" (the naval operations plan) and "Overlord". That was the last straw, and the author of the puzzles, a schoolteacher named Leonard Dawe, was arrested and interrogated. The investigators finally concluded that the appearance of the words was just a coincidence. The event has been so described in histories, and has even been used as an illustration of how seemingly meaningful events can arise out of pure coincidence.

According to National Geographic, though, in 1984 the schoolteacher revealed that one of his students had picked up the words while hanging around army camps. When the teacher had asked his students to provide unusual words as ingredients for his puzzles, he had innocently passed them on.

Roger Squires of Ironbridge, Shropshire is the holder of the record for the World's Most Prolific Crossword Compiler, currently, April 2006, having had over 65,000 published crosswords appearing in over 470 outlets including over 70 abroad. He also holds the record for the longest word to have appeared in a published crossword, the place in Wales Llanfairpwllgwyngyllgogerychwyrndrobwllllantysiliogogogoch (58 letters) clued as an anagram. His millionth clue appeared in the Daily Telegraph in September 1989. He is one of only four compilers to have appeared regularly in all the UK quality newspapers.

Crossword puzzles in Philosophy

American philosopher of science Susan Haack has offered the crossword as a possible model for the workings of science:

The best model of is not, as much recent epistemology has assumed, a mathematical proof, but a crossword puzzle. The clues are the analogue of experiential evidence, already-completed entries the analogue of background information. How reasonable an entry in a crossword is depends upon how well it is supported by the clue and any other already-completed intersecting entries[. (Manifesto of a Passionate Moderate, p. 95)

Haack goes on to extend the analogy to show how it quite naturally fits some of the features of science that otherwise seem troubling (for example, Thomas Kuhn's paradigm shifts.

Notation

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A notation has evolved to allow crosswords to be rendered compactly, and enjoyed by the blind or partially sighted.

It consists of giving the locations of the black squares in each row as letters (A=1,B=2, etc.), e.g. for the example crossword above:

1. D E
2. B D E
3.  
4. A B D
5. A B

Although the numbering scheme could be consistently applied from this information, it is customary to quote the starting square of each clue in (number-letter) format to assist the solver.

See also

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A puzzle commonly called the numerical equivalent of a crossword:

• Cross Sums

Board games based on the crossword concept:

• Scrabble
• Upwords

Aids to solve crosswords include:

• Dictionaries
  • Biographical dictionaries
  • Rhyming dictionaries
• Gazetteers
• Encyclopedias
• Almanacs
• Thesauri

External links

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