Bigram forms have two letters per space rather than the usual one. See the example in the square description.
Most forms have the same words across and down. Forms whose across words are different from the down words are called “double forms.” When a square, for example, has different words across and down, it is termed a “double square.” (Forms that inherently have different words across and down, such as pyramids, are not called double.) Double forms are harder to create than standard forms. See the examples in the diamond and square descriptions; other shapes shown in this Guide as single can also be constructed as double.
A hollow form has the same shape as the usual example of that form, but with a small section missing from the middle. The missing section is a smaller version of the form’s shape. Hollow forms have several lines that contain more than one word. See the example in the diamond description.
For forms that can be created in various orientations, such as halfsquares and enneagons, “left” and “right” describe which way the words slant. In left forms, the words appear to flow from top left to bottom right; in right forms, they flow from top right to bottom left. See the word after “left” or “right” in the title for an example.
Usually seen as squares, progressive forms consist of successive words that differ by only one letter. The first word is beheaded and has a new letter added to its end to make the second word, and so on throughout the form. See the example in the square description.
Usually seen as squares, all the forms in a sequential set contain a certain word, which will be seen as the first word in the first form, the second word in the second form, and so on until it has appeared in each position once. See the example in the square description.
Something Different forms are described in the Extras section of the Guide.
Trigram forms have three letters per space rather than the usual one. See the example in the square description.
In a truncated pyramid or pyramid variation (such as a pyramidal windmill), the pyramid’s base is an even number of letters; thus, the shortest word is two letters long rather than one. See the example in the pyramid description.
In most forms, the solver fills in one letter per space. In a variogram form - most often a square - a space might contain just one letter, or might contain any number of letters more than that. Bigram and trigram forms are specific cases of a variogram form. See the example in the square description.
Variogram forms are often significantly harder than standard forms. Generally, it is best to clue them as straightforwardly as possible.
Formists sometimes compose variogram squares to incorporate some specific idea; for example, to include the sequence NPL in a number of places, or to have a pattern in the number of letters used in each space.
In a space where a word crosses itself-such as the first space in a square-having a long multiletter sequence can be problematic for solvers. Multiletter sequences should generally be included in two words.
In a vowelless form, the answers to the clues must have their vowels removed before they will fit in the shape; similarly for consonantless forms. In these forms, Y is always considered a vowel.
Because each answer provides less information to the solver than usual, it is best to clue the entries as straightforwardly as possible. The forms editor will sometimes provide extra information, such as enumerations for any phrases, or NI2/NI3 tags.
See the examples in the square description.