Abbreviated Guide to Flats

This page is an overview of the NPL Flat Types. Puzzle types marked with an asterisk (*) are recent additions and not covered by the Online Guide to the Enigma. The upcoming edition will probably incorporate these new puzzles.

Puzzle TypeDescriptionSamples
Acrostical enigma (AE) A word combines with initial letters from each clue to create new words. See guide.
Alternade A word or phrase is divided into two or more others by taking alternate letters in order. schooled → shoe + cold;
lacerated → let + are + cad
Ambigram An anagram or antigram, depending on personal opinion. See guide.
Anagram An appropriate transposal. is tempo, sirs ~ prestissimo
Antigram An opposite transposal. the budgerigar ≠ great huge bird (it's a parakeet)
Backswitch A word or phrase becomes another when its last letter is changed (or "switched") and the remaining letters are reversed ("turned back"). See also Switchback. autumn → mutual; dragnet → en garde
Baltimore deletion Each letter in turn is removed to form a new word. peat → eat, pat, pet, pea
Baltimore transdeletion A word or entry phrase is turned into a series of others by removing each letter in turn and rearranging the rest. baker → rake, kerb, bare, bark, beak
Beheadment A word or phrase becomes another when its first letter is removed. usable → sable; aspirate → spirate → pirate → irate → rate → ate
Brookline letter-change A word or phrase changes each one of its letters in turn to make others. rice → nice, race, rile, rich
Change of heart A change of heart is similar to a Double-Cross in that two words or phrases switch a letter or string of letters, but the things being switched aren't necessarily located at the ends of words. share + colt → sole + chart
Changeover A word or phrase becomes another when one letter changes to another and moves to another location. goatherd → gathered (2nd to 7th)
Charade A word or phrase is broken into two or more shorter ones. outreached → outre + ached
Combination padlock A padlock, with the added feature that overlapping the two words produces a fourth word or phrase. scar + Arab → scarab → scab
Consonantcy Two or more words or phrases share the same consonants in the same order, with any number of vowels (incl. Y). acorn ~ crayon ~ ocarina; begin ~ beguine ~ begonia
Curtailment A word or phrase becomes another when its last letter is removed. stingy → sting
Deletion A word or phrase becomes another when an interior letter is removed. simile → smile
Double Acrostical Enigma (AE) An AE with two solutions. Seeguide.
Double-cross Two words or phrases are each divided into two pieces; then their second pieces are switched to form two others. maids + rapture ~ mature + rapids
[ma/ids, rap/ture]
Dropout Two words are joined; then one word is dropped out to form another from the leftover letters. reamer + itch → reach + merit
[rea(mer, it)ch]
Enigma A word or phrase is clued indirectly through wordplay. Generally, a riddle describes a thing and an enigma a word. See guide.
Enigmatic rebus Enigmatic is a red flag, warning you that the reading involves something other than simple manipulation of letters. See guide.
False derivatives A word or phrase becomes another when some grammatical change is inappropriately applied. limb → limber (false comparative);
treat → retreat (false reiterative);
butter → buttress (false feminine, analogous to waiter → waitress)
FWNFR "Flats we never finish reading" were added to the guide in 2004. See guide
Head-to-tail shift A word or phrase becomes another when its first letter is moved to its end. emanate → manatee
Heart transplant In a heart transplant, a letter or series of letters is taken from inside one word and transplanted to another. clear + wild → car + willed
Heteronym Two words or phrases with the same spelling are used with different pronunciations and meanings. mustache ~ must ache
Homoantonym Two words or phrases sound like two other words that are antonyms. knights, daze (sounds like nights, days)
Homoconcominym Two words or phrases sound like two other words or phrases that form a familiar pair. hart, sole (sounds like heart, soul)
Homonym Two or more unrelated words or phrases are pronounced the same but spelled differently. hair ~ hare
Homosynonym Two words or phrases sound like two other words that are synonyms. soul, loan (sounds like sole, lone)
Interlock Two or more shorter words or phrases are interlocked to form a longer one. (But not in a regular pattern like the alternade.) fig + rebus → firebugs
Letter bank A word or phrase (the "bank") is chosen that has no repeated letters. One or more longer words or phrases are formed, each using all the letters in the bank at least once and as many more times as needed. lens → senselessness; manicures → Neiman Marcus, American sumac, marine insurance
Letter change A specified letter is changed to make a new word or phrase. 3rd letter: pastry ~ pantry
Letter shift A word or phrase becomes another when one letter is shifted to a new position. Proust ~ sprout
Linkade A word or phrase is broken into two or more shorter parts, which overlap by exactly one letter. libraries → Libra + Aries
Literatim Words or phrases are composed by pronouncing the letters of a base word individually or in combinations. vacations → essay (SA) + ivy (IV) + eighty (AT) + envy (NV)
Metathesis A word or phrase becomes another when two letters are interchanged. converse ~ conserve
Mutation A transposal that is only vaguely appropriate or even entirely inappropriate. See guide.
Mynoreteh A reversed heteronym. won ton ~ not now
Padlock The last two or more letters of a word or phrase are the same as the first two or more letters of another; joining the remaining letters forms another (the lock). norther + thermal → normal
Palindrome A sentence or phrase is spelled the same forward as backward. Draw pupil's lip upward
Phrase Shift In a phrase shift, an adage, well-known quotation, or cliche is remade by shifting a letter from one word to another. The buck sops there; don't give UPS the hip
Rebade A hybrid of the rebus and alternade. See guide.
Rebus A word or phrase is represented by letters, numbers, or symbols; their positions; and sometimes related letter-play, like alterations to the verse. See guide.
Repeated letter change A word or phrase becomes another when one letter is changed to another letter wherever it appears. The letter must appear at least twice and the change must be reversible. crochet ~ prophet; skunk ~ stunt ~ sauna
Repeated letter or Word deletion A word or phrase becomes another when one letter or word is removed wherever it occurs. bassist − S → bait; prospered − P → rose-red; had it made − ad → hit me
Reversal A word or phrase becomes another when reversed. desserts ~ stressed.
Reversed puzzles A variation of a puzzle in which you have to reverse the result to read the final solution. See guide.
Riddle Something is described enigmatically in verse. Generally, a riddle describes a thing and an enigma is a word. See guide.
*Rochester transaddition Each letter in a baseword is added back to the word and the result transposed.
nacre → canner, arcane, cancer, craner, careen
Sound change One sound is changed in a word or phrase to make another. legroom ~ legume
Sound shift A word or phrase becomes another when its first sound is moved to its end. ciao → ouch
Spoonergram A phrase or word becomes another when the initial consonant sounds in its component words (or stressed syllables) are swapped. Word boundaries do not need to be preserved. key ring ~ reeking; trained seal ~ strained eel; rake over the coals ~ cake over the rolls
Subade A hybrid of the suber and alternade or a reversed rebade. See guide.
Suber A reversed rebus. See guide.
Switchback A word or phrase becomes another when its first letter is changed, or "switched", and the remaining letters are reversed, or "turned back". See also Backswitch. hydra → tardy
Terminal deletion A word or phrase is changed to another by removing its first and last letters. foregone → Oregon
Transaddition This flat type is always classified as a transdeletion.  
Transade A transposed charade. A word or phrase is broken up into two or more shorter parts. Each shorter part is transposed (separately) to make a word. solu + tion → soul + into
Transdeletion A word or phrase becomes another when one letter is deleted and the others are transposed. There must be at least four parts and simple deletions are not used. righteous − I → roughest - E → troughs − R → sought − U → ghost − G → shot − S → tho
Transpogram A word or phrase becomes another when divided into two parts, which are interchanged. rock-hard ~ hard rock; alloy ~ loyal
Transposal A word or phrase becomes another when its letters are rearranged. A flat is only classified as a transposal when it doesn't match a specific transposal type, such as metathesis, reversal or transpogram. [NOTE: A transposal is commonly called an anagram outside the NPL. In the NPL, an anagram is always an appropriate transposal.] sleuth ~ hustle
Word deletion A word or phrase is deleted from a longer one, leaving another word or phrase. In a multi-word deletion, two or more consecutive words are deleted. In a progressive word-deletion, three or more words are nested to form a longer one. performance − man → perforce; organgrinder − gang rin → order; consecratory − Ra − sector → cony

Word substitution A word or phrase is replaced by another in a longer one, producing a different word or phrase. progress ~ congress [pro/con-gress];
Puzzle TypeDescriptionSamples
*Antonym puzzles A puzzle variation using antonyms. For example, in an antonym substitution, replace a word with its antonym. progress ~ congress (antonym substitution)
Bigram puzzles Two-letter groups (bigrams) are the basic unit of these puzzles. seraph ~ phrase (bigram reversal); we're aka Krewe (bigram palindrome)
Group puzzles Each of the answer words or phrases is related to a member of a well-known group in the manner of a specified flat type. sate, stew, shout, thorn ~ east, west, south, north (transposal group)
Phonetic puzzles Puzzle variations in which sounds are the basic unit instead of letters. quest → west (phonetic beheadment)
Progressive puzzles A sequence of three or more of a given flat type. padre, retrench, trenchant, anthem, hemlock, padlock (progressive padlock)
*Synonym puzzles A puzzle variation using synonms. For example, in a synonym deletion, a synonym of the main base word has letters which are a subset of the letters in the main word. Remove those letters, and what remains, in that order, spells the second word. The synonym might be a synonym for a sense of the main word other than the one used in the flat. For a synonym substitution, replace a word with it's against − anti → gas (synonym deletion)
Trigram puzzles Three-letter groups (trigrams) are the basic unit of these puzzles.  
Puzzle TypeDescriptionSamples
*Alterposal Alternate letters are taken from a word or phrase. Each set of letters is then transposed into another word. lambskin → slim, bank
*Bridgewater transaddition A generalization of the Rochester Transaddition. You begin with an n-letter BASE word and an m-letter BANK word (note: n and m do not need to be equal, as they are here). The other solwords, numbered ONE though M, are formed by transposing _all_ the letters in BASE plus each of the m letters from BANK in turn (so it's nice if BANK is an isogram). Another example: BASE = cast iron, BANK = atone, ONE = raincoats, TWO = tractions, THREE = consortia, FOUR = transonic, FIVE = creations.
cast iron + atone → raincoats, tractions, consortia, transonic, creations
*Convergence A word or phrase is broken down into a series of shorter words and phrases by taking letters in order from the the original phrase - one from the front, then one from the back, then one from the front, and so on.
sapwort → star + pow
*Hutto transdeletion A word or phrase has every possible pair of letters deleted, and each time the resulting set of letters is transposed to form another word. The cuewords in the following example indicate which pair of letters has to be deleted; the original word must also appear in the flat. This flat type generates a very large number of solution words: a base word of length 5 would require eleven; the example given has a seven letter base word, which results in twenty two words to be clued. tirades → 12 dares, 13 ideas, 14 rides, 15 raise, 16 raids, 17 aired, 23 stead, 24 drest, 25 rates, 26 darts, 27 tread, 34 deist, 35 iteas, 36 staid, 37 Edita, 45 rites, 46 strid, 47 tried, 56 stair, 57 irate, 67 triad
*Lakeway changeover A set of words such that any two of them form a changeover base, with every possible letter position included. that, heat, hart, hats
*Letter Bankless A letter bank where the minimal set of letters is not included in the base. This is most likely to be done because the minimal set will not transpose into a word. green around the gills ~ Thousand Island dressing
*Lock & Drop A lock and drop is like a padlock, except that in addition, the overlapping letters form a word.
lethal + halter → Hal + letter
*Multiple repeated-letter deletion Like a repeated-letter deletion, except that all occurrences of any repeated letters are deleted. statism → aim; catacomb → tomb
*Mutual replacement Two letters replace each other each time they appear in a word.
sell → less; travail → trivial
*Name Change A substring of one word is a proper name and is replaced by another proper name to form another word. The proper names are not individually clued. Avalon → Avedon (Al → Ed); camel → cachet (Mel → Chet)
*Permuted consonantcy In the Permuted Consonantcy, all permutations of the consonant letters appear once. For example, in a three-consonant flat, with all consonants different (which the following example is), the six squares might, in order, contain the following consonant sequences:
Consonants might also be repeated:
eclair, cairo IL, ulcer, lyric, oracle, relic
*Reduplication The base of a reduplication is such that the letters in the first half are repeated in the second half. edit|ed it; Saint Theresa in the len|s. Ain't there Saint Helen
*Split Shift In a split shift, two (or more) of the base words start and end with identical sequences of letters. Linking the dissimilar parts makes another word. elegant + element → game
*Terminal letter change The first and last letters of a word are both changed. Spiderman ~ epidermal
*Terminal Rotation A pair of words becomes another pair of words when all four terminal letters shift position in a manner analogous to rotating tires on a car: each front letter moves to the end, while the back letters move in front and switch words. tend + bums → sent + dumb
*Trans-cross A trans-cross is similar to a double cross, but the pieces of the word switch AB, CD, AC, BD. seal + rely → sere + ally
*Transinterlock An interlock in which one of the shorter pieces is tranposed. ? an immediate action / a meditation / cinema

Most examples are taken from the Guide, where appropriate credits are given.

"~" is used for symmetric relationships; "→" is used for asymmetric ones; "+" indicates the words that are manipulated together; "," indicates they are not; "−" indicates deletion

This page was last updated on Thursday, June 18, 2015. /webmaster