The crossword is the most common variety of word puzzle in the world. Modern crosswords 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 (commonly called "blanks") have no letters, and are used to separate words (all contiguous blocks of white squares spell words or phrases). Squares in which answers begin are numbered, left to right, top to bottom. The clues are then referred to by these numbers (ambiguities are resolved by the common practice of referring to clues by both number and 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, although in many widely distributed American crosswords such as the New York Times this is often omitted.
Types of Grid
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.
Another tradition in puzzle design (in North America 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. In addition, 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.
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.
In 1968 and 1969, composer and lyricist Stephen Sondheim published an inventive series of crossword-like puzzles in New York magazine. The Atlantic Monthly regularly features a crossword-like "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.
Another crossword type is the diagramless crossword. The grid offers overall dimensions, but it is unnumbered and the black squares' locations 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 outlines suggesting other shapes.
French language crosswords are smaller 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.  (http://homepage.urbanet.ch/cruci.com/textes/histoire6.htm)
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. In French-language puzzles, diacritics are omitted for similar reasons (e.g. the initial Ê of answer ÊTRE could double as the final É of CONGÉ when written ETRE and CONGE).
Types of Clues
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:
- 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 placenames. For example, SSE might be clued as "New York to Washington direction".
- 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."
- Fill-in-the-blank clues are often the easiest in a given puzzle, and a good place to start solving. Ex.: "__ Boleyn" = ANNE
- 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).
- 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.
Many 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:
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., BERMUDA); 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.
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 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. Examples of this could be Dimmer, Allies would make Demoralise or You, ill, never, whore, Cologne 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.
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).
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 parantheses 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.
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.)
In Translation Crosswords, the clue is given in a foreign language. This makes them an entertaining vocabulary trainer. An example of Translation Crosswordscreated (http://www.translationcrosswords.com) 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 (http://www.yourdictionary.com/crossword/index.html).
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.
A small example of a quiz-style crossword, to illustrate the format:
Sheep sound (3)
3. Neither liquid nor gas (5)
5. Humour (3)
Road passenger transport (3)
2. Permit (5)
4. Shortened form of Dorothy (3)
The solution to this crossword is:
On December 21, 1913, Arthur Wynne published a 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 (http://www.crosswordtournament.com/more/wynne.html), is frequently cited as the first crossword puzzle, and Wynne as the inventor.
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.
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. Since 1993, they've 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  (http://www.crosswordtournament.com).
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 (http://magma.nationalgeographic.com/ngm/0206/feature1/), 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.
It consists of giving the locations of the black squares in each row as letters (A=1,B=2, etc.), eg for the example crossword above:
- D E
- B D E
- A B D
- 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.
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.
Crosswords in other languages
Although the crossword is an English-language invention and predominately an English-language exercise, crosswords are not uncommon in other countries, with clues and entries in other languages. It is common for diacritical markings in such languages to be ignored when placing entries into the solution grid. Particularly curious is the Japanese 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.
- Daily Translation Crosswords (http://www.TranslationCrosswords.com/)
- The Hindu Crossword Yahoogroup (http://groups.yahoo.com/group/thehinduxword/)
- Daily solutions to The Hindu Crossword (http://vinodraman.blogspot.com/)
- Crossword Puzzles (http://www.crossword-puzzles.co.uk)
- Play one of seven Online Daily Crossword Puzzle Games (http://www.todayscrossword.info)
- Crosswords (by Ray Hamel) (http://www.primate.wisc.edu/people/hamel/cp.html)
- Crossword Puzzles for students of English (http://membres.lycos.fr/jeuxdelettres/)
- Online word searching tool (http://wims.unice.fr/wims/wims.cgi?module=tool/lang/wfind.en)
- OneAcross.com Crossword Clue Solver (http://www.oneacross.com)
- WordFind - program to find words, anagrams and palindromes (http://www.andyscouse.com/pages/wordfind.htm)
- American Crossword Puzzle Tournament (http://www.crosswordtournament.com/)
- Why are crossword puzzles symmetrical? (http://www.straightdope.com/classics/a2_174b.html) (from The Straight Dope)
- Website for those interested in creating their own crosswords (http://www.cruciverb.com/)
- Coded Cross-words The crosswords with no clues, but coded numbers help to solve the puzzle (http://word-games.yoogi.com/ccw/)