Isomorph
All words have the same cryptogram pattern, so that if they were encrypted it would be impossible to tell them apart. Examples: opponent, irritate, foofaraw; and Harry S. Truman, well-tailored.
Isomorphs are tricky to solve—getting one word may not give a lot of information about another. Be sure to clue each word carefully.
By analogy with letter banks, each isomorph word should have significant repetition: the word length should be at least three more than the number of distinct letters. The editor may waive this rule for a clever, well-clued base (for example, Next Lingo once wrote an isomorph on dermatoglyphics, uncopyrightable). Unlike letter banks, there is no note when the rule is waived (since that information might spoil the solution).
Another useful guideline is that the words shouldn’t share a letter in the same position (e.g., the common “p” in pepper, pippin); one word should be able to represent the other in a cryptogram. The more parts the isomorph has, the less this rule is applied; the editor might well allow lollop, mammal, pepper, pippin.
The isomorph was invented by Treesong.