What are the word records for number of different letters?

[ Editor: from the Taxonomy of Wordplay, www.questrel.com, retrieved 28 Oct 2026. Classes (common, uncommon, hyphenated words, phrases), scores, ties (-t) and the source codes in brackets are explained in language/english/word.records.introduction. ]

a.  isogram (all letters different), longest [L296,7-33,9-54,18-67]
        common word: uncopyrightable (15)
b.  pair isogram (each letter occurs two times), longest [L14,128,1-201,4-136,142,5-25,111,205,6-13,212,7-33,15-136,16-156,219,18-140]
        common word: intestines (10)
        uncommon word: scintillescent (14)
c.  trio isogram (each letter occurs three times), longest [7-33,88,15-138,18-140,23-28]
        common word: deeded (6)
        uncommon word: sestettes (9)
        hyphenated word: blah-blah-blah (12)
d.  tetrad isogram (each letter occurs four times), longest [1-142,18-140]
        uncommon word: kukukuku (8)
e.  polygram (each letter occurs more than once), longest [5-49,110]
        common word: reengineering (13)
        uncommon words: transistorisations, unprosperousnesses (18-t)
        phrase: intestinal calculuses (20)
f.  geometric shapes [3-109,5-236,13-176,213,15-109,125,154]
        i.  pyramid word (one letter occurs once; one letter occurs twice; etc.), longest
                common words: evennesses, keennesses, sanenesses, sereneness, sleeveless (10-t)
                hyphenated word: dead-endednesses (15)
        ii.  tetrahedron word (one letter occurs once; two letters occur twice; etc.), longest
                common word: instantiations (14)
        iii.  reverse tetrahedron word (one letter occurs four times; two letters occur three times; etc.), longest
                uncommon words: argillaceocalcareous, autosuggestibilities, counterassassination, countertransferences, existentialistically, inappreciativenesses, interesterifications, semicapitalistically, teleutosporiferouses, ultraminiaturization (20-t)
g.  ratio length to letters, highest
        common word: senselessnesses (3.75)
        uncommon word: kukukuku (4)
        hyphenated words: pip-pip-pip, tat-tat-tat (4.5-t)
        phrase: yadda yadda yadda (5)
h.  ratio length to letters, highest non-tautonym [L158,298]
        common word: senselessnesses (3.75)
        hyphenated words: pip-pip-pip, tat-tat-tat (4.5-t)
        phrase: yadda yadda yadda (5)
i.  ratio length to letters, lowest for each length
        see list "Word with the Lowest Ratio Length to Number of Different Letters for Each Length" below
j.  different letters, most [M56]
        common word: uncopyrightable (15)
        uncommon words: blepharoconjunctivitis, carbomethoxyglycines, dimethyltubocurarines, diphenylthiocarbazones, mandibulopharyngeals, phenylthiocarbamides, pseudolamellibranchiata, pseudolamellibranchiate, psychogalvanometric, ... and 4 others (16-t)
        phrases: computerized axial tomography scanner, rocky mountain flowering raspberry (19-t)

Word with the Lowest Ratio Length to Number of Different Letters for Each Length
--------------------------------------------------------------------------------
16        common word: phenylketonurics (1.14)
        uncommon words: ventriculography, pulmobranchiates (1.06-t)
17        common words: comprehensibility, neuropsychologist, microencapsulated, deoxyribonuclease, uncomprehendingly (1.21-t)
        uncommon words: diacetylmorphines, entwicklungsroman, hydrobasaluminite, hyperconjugations, pterygomandibular (1.13-t)
        phrases: buckthorn families, pitch nodule makers (1.06-t)
18        common words: oversimplification, neurophysiological, neuropsychological, neuropsychologists (1.28-t)
        uncommon words: carboxyhemoglobins, entwicklungsromane, hydrobasaluminites, hyperglobulinemias, pseudoromantically, psychogalvanometer, triphenylformazans, ventriculographies (1.2-t)
        phrase: hydromagnetic waves (1.12)
19        common words: oversimplifications, incomprehensibility (1.35-t)
        uncommon words: psychogalvanometric, superacknowledgment (1.18-t)
20        common words: magnetohydrodynamics, radiopharmaceuticals (1.42-t)
        uncommon words: carbomethoxyglycines, mandibulopharyngeals, phenylthiocarbamides, superacknowledgement (1.25-t)
21        common word: psychoneuroimmunology (1.5)
        uncommon words: dimethyltubocurarines, superacknowledgements (1.31-t)
22        common words: counterrevolutionaries, electroencephalography (1.83-t)
        uncommon words: blepharoconjunctivitis, diphenylthiocarbazones (1.37-t)
        phrase: calcium hydrogen sulfite (1.29)
23        common word: dichlorodifluoromethane (1.64)
        uncommon words: pseudolamellibranchiata, pseudolamellibranchiate (1.43-t)
        phrases: calcium hydrogen sulfites, double wingback formation, qualified majority voting (1.35-t)
24        uncommon word: blepharoconjunctivitises (1.5)
        phrases: double wingback formations, public works and ways system (1.33-t)
25        uncommon word: spectroheliokinematograph (1.66)
        phrase: public works and ways systems (1.38)

-- Taxonomy of Wordplay, www.questrel.com

[ Editor: on the longest isogram, from a thread "Word-game type
questions" in rec.puzzles.crosswords, alt.usage.english and
rec.puzzles, February 1995. ]

wskdpl@puknet.puk.ac.za (Laurie, DP) writes:
> "pubvexingfjordschmaltzy, adj.  Pertaining to the overly sentimental
> aspects of Norwegian scenes that annoy British beer drinkers"
>
> BTW, I didn't make up that 23-letter word, I saw it somewhere.

rsa@swindon.gpsemi.com writes:
> Dmitri A. Borgmann's "Language on Vacation". [...]
>
> But seriously, folks: the longest *real* (non-Borgmann) English isogram is
>
> dermatoglyphics
>
> If your favourite dictionary doesn't have that, how about
>
> ambidextrously
>
> If it doesn't have that either, time to buy a better dictionary.

Martin Gardner addressed this puzzle in one of his hundreds of columns.
I think the other 15-letter example "uncopyrightable" is also from that
column, and can arguably be extended to "uncopyrightables".  Gardner
also suggested the fictitious "vodkathumbscrewingly" (20); is Borgmann
also responsible for that one?

Michael Reid pointed out a few years ago that "hyperosculating" (which
arises in algebraic geometry) happens to be another such 15-letter
word.

-- Noam D. Elkies <elkies@math.harvard.edu>