Forms are puzzles similar to crosswords; from given clues, the solver fits words into a pattern. The important difference is that form patterns are geometrical shapes and have no black squares, as crosswords do.
If the form is a shape described in this section, no blank diagram will be shown in The Enigma. The title and number of clues will be sufficient information to determine the form's shape exactly. For example, if the title is "SQUARE" and there are six clues, the words will be filled into a shape six squares across by six squares down. (This form would be called a 6-square. Forms' sizes are named for the length of their longest entries.) If the form is a shape not shown in this section, the editor will usually print a diagram showing the shape.
(Occasionally, the editor may also describe a new form type's shape via form notation; for example, a wedge-shaped form could be described as S:R. You will never be required to understand this notation to solve a form, but if you are interested you can find more details here.)
Forms are most popular when they consist mainly of common words and phrases. Often, though-particularly in larger forms-the form constructor (or formist) might need to resort to unusual words to finish the form. Form words may come not only from the standard NPL references but from any English-language source. Solvers may get credit for incompletely solved forms containing words not found in any standard NPL reference and not easily inferable from context. (While formists are allowed to use these words, form solvers are not always required to find them.)
Historically, formists were not allowed to use abbreviations, partial phrases (for example, ETAT clued as "Coup d'___"), or foreign words. In recent years, Enigma forms have contained all of these. Some people (myself included) do not consider forms containing these sorts of entries to be legitimate; others, seeing forms as similar to crosswords, have no problem with them. Formists must decide this question for themselves.
Prohibited words include all those listed in NI2 only as "reformed spelling." The reformed spelling movement was a brief, unpopular phenomenon, and while the NI2 editor was trying to popularize those spellings by including them, they never gained wide acceptance. For this reason, formists have never felt free to use those spellings, and they are banned from all types of Enigma puzzles.
Here are explanations for many of the tags currently used in forms. A number after any of these abbreviations indicates the edition used; for example, (OED2) designates the second edition of the Oxford English Dictionary.
AH: American Heritage Dictionary
of the English Language
Amende: Random House Famous Name Finder, by Coral Amende
B&M: The Complete Directory to Prime Time Network and Cable TV Shows, by Tim Brooks and Earle Marsh
BIP: Books In Print
Cham.: Chambers 20th Century Dictionary
Col. Enc.: Columbia Encyclopedia
Coll.: The collegiate form of the reference mentioned. For example, (RH Coll.) designates the Random House Collegiate Dictionary.
EB: Encyclopaedia Britannica
EWED: Encarta World English Dictionary
Lipp. Bio.: Lippincott Biographical Dictionary
Lipp. Gaz.: Lippincott Geographical Dictionary
Maltin: Leonard Maltin's Movie & Video Guide
MW Bio: Merriam-Webster New Biographical Dictionary
MW Geo: Merriam-Webster Geographical Dictionary
NW: Webster's New World Dictionary
OED: Oxford English Dictionary
RH: Random House Dictionary of the English Language, Unabridged
TIG: Times Index Gazetteer
WA: World Almanac
WB Enc.: World Book Encyclopedia