20 letter words are where English runs out of everyday vocabulary. A few still land in normal use, like internationalization in business writing and electroencephalogram on a hospital chart. Past that handful, almost every word this long names a chemical compound or a medical procedure.
List Of 20 Letter Words
P dominates the set, with more than a hundred words to itself, followed by C, A, E, and H. At the other end four letters produce nothing at all, since none of them begins with J, W, Y, or Z. From Q come only number names such as quadringentillionths. Because the alphabet thins as words lengthen, W still works at 18 letters and has disappeared by 19.
20 Letter Words Starting With A
- Abdominohysterectomy
- Abetalipoproteinemia
- Abetalipoproteinemic
- Acetylaminofluorenes
- Acetylcholinesterase
- Acetylmethylcarbinol
- Adenomyoepitheliomas
- Adrenocorticosteroid
- Adrenocorticotrophic
- Adrenocorticotrophin
- Adrenocorticotropins
- Adrenoleukodystrophy
- Allotransplantations
- Aminoethylcarbazoles
- Aminopolysaccharides
- Anarchoindividualist
- Anatomicophysiologic
- Angiocardiographical
- Angiocardiographists
- Anthropobiologically
- Anthropocentricities
- Anthropogeographical
- Anthropomorphisation
- Anthropomorphization
- Anthropomorphologist
- Antiauthoritarianism
- Anticapitalistically
- Anticonservationists
- Anticonventionalists
- Antienvironmentalism
- Antienvironmentalist
- Antiestablishmentism
- Antifluoridationists
- Antifundamentalistic
- Antiinstitutionalist
- Antiinsurrectionally
- Antiinsurrectionists
- Antiparliamentarians
- Appendicoenterostomy
- Archaeolithothamnium
- Archaeometallurgical
- Arthroophthalmopathy
- Autodepolymerisation
- Autodepolymerization
- Autohaemotherapeutic
- Autolithographically
- Autophosphorylations
- Autoradiographically
- Autosuggestibilities
- Autotransplantations
- Azoisobutyronitriles
20 Letter Words Starting With B
- Bacteriochlorophylls
- Ballistocardiographs
- Ballistocardiography
- Barothermohygrograms
- Barothermohygrograph
- Barytolamprophyllite
- Benzofuroquinoxaline
- Benzophenanthrolines
- Buckminsterfullerene
20 Letter Words Starting With C
- Characteristicalness
- Chemicopharmaceutics
- Chemicophysiological
- Chemicophysiologists
- Chemoautotrophically
- Chemostratigraphists
- Chemotherapeutically
- Chemotherapeuticness
- Chlorofluoromethanes
- Cholecystenterostomy
- Cholecystgastrostomy
- Cholecystnephrostomy
- Chromolithographical
- Chronostratigraphers
- Chronostratigraphics
- Chronostratigraphist
- Compartmentalisation
- Compartmentalization
- Comprehensiblenesses
- Comprehensivisations
- Comprehensivizations
- Contradistinguishing
- Conventionalizations
- Corynebacteriophages
- Counterconditionings
- Counterdemonstraters
- Counterdemonstrating
- Counterdemonstration
- Counterdemonstrators
- Counterintelligences
- Counterintuitiveness
- Countermobilisations
- Countermobilizations
- Counterpropagandized
- Counterpropagandizes
- Counterrevolutionary
- Counterrevolutionist
- Countersurveillances
- Crystallographically
20 Letter Words Starting With D
- Decahydronaphthalene
- Decentralisationists
- Decentralizationists
- Deepithelialisations
- Deepithelializations
- Defunctionalisations
- Defunctionalizations
- Dehydrochlorinations
- Deindividualisations
- Deindividualizations
- Deindustrialisations
- Deindustrializations
- Deinstitutionalisers
- Deinstitutionalising
- Deinstitutionalizers
- Deinstitutionalizing
- Deoxycorticosterones
- Deoxyribonucleotides
- Departmentalizations
- Dermatofibrosarcomas
- Desentimentalisation
- Desentimentalization
- Desoxycorticosterone
- Deterritorialisation
- Deterritorialization
- Dichloromethylphenyl
- Dichlorophosphazines
- Diethylstilboestrols
- Distinguishabilities
20 Letter Words Starting With E And F
- Electrocardiographer
- Electrocardiographic
- Electrocatalytically
- Electrocauterisation
- Electrocauterization
- Electrochronographic
- Electrocommunicating
- Electrocommunication
- Electrocommunicators
- Electrocontractility
- Electrocorticography
- Electroencephalogram
- Electrogalvanisation
- Electrogalvanization
- Electrohydraulically
- Electrohydrodynamics
- Electroluminescences
- Electromagnetisation
- Electromagnetization
- Electrometallurgical
- Electrometallurgists
- Electronystagmograph
- Electrooculographies
- Electrooculographist
- Electrophotographies
- Electrophysiological
- Electrophysiologists
- Electropneumatically
- Electroretinographic
- Electrosynthetically
- Electrotherapeutical
- Existentialistically
- Forethoughtfulnesses
- Fundamentalistically
20 Letter Words Starting With G
- Galvanocauterisation
- Galvanocauterization
- Gastroduodenostomies
- Geomicrobiologically
- Glomerulonephritides
20 Letter Words Starting With H
- Hemangioendothelioma
- Hepaticoduodenostomy
- Hepatoduodenostomies
- Heterobasidiomycetes
- Heterosexualisations
- Heterosexualizations
- Hexachloroantimonate
- Hexamethylphosphoric
- Histocompatibilities
- Histoincompatibility
- Histomorphologically
- Historicogeographies
- Homeotransplantation
- Homotransplantations
- Hydrochlorothiazides
- Hydrocinnamaldehydes
- Hydrodesulfurization
- Hydrometallurgically
- Hydroxyanthraquinone
- Hydroxylpyromorphite
- Hydroxytetracyclines
- Hymenopterologically
- Hyperadrenocorticism
- Hyperbrachycephalics
- Hyperbrachycephalous
- Hypercholesterolemia
- Hypercholesterolemic
- Hypercoagulabilities
- Hyperconsciousnesses
- Hyperdolichocephalic
20 Letter Words Starting With I
- Immunocytochemically
- Immunohistochemicals
- Immunohistochemistry
- Immunopathologically
- Immunoprecipitations
- Inappreciativenesses
- Incommensurabilities
- Incomprehensibleness
- Inconsequentialities
- Inconsiderablenesses
- Incontrovertibleness
- Indestructiblenesses
- Indiscriminatenesses
- Indistinguishability
- Institutionalisation
- Institutionalization
- Instrumentalisations
- Instrumentalizations
- Intellectualisations
- Intellectualizations
- Interchangeabilities
- Intercommunicability
- Intercommunicational
- Interconnectednesses
- Interconvertibleness
- Intercrystallisation
- Intercrystallization
- Intergenerationality
- Internationalization
20 Letter Words Starting With K And L
- Keratoconjunctivites
- Keratoconjunctivitis
- Laryngopharyngectomy
- Laryngotrachectomies
- Lepidopterologically
- Lipochondrodystrophy
- Lithostratigraphists
- Lymphogranulomatoses
20 Letter Words Starting With M
- Macromorphologically
- Macrostratifications
- Magnetofluiddynamics
- Magnetohydrodynamics
- Magnetostratigrapher
- Magnetostratigraphic
- Meningoencephalocele
- Metadichlorobenzenes
- Metallotherapeutical
- Microcinematographic
- Microcolourimetrical
- Microcrystallinities
- Microcrystallography
- Microelectrophoreses
- Microelectrophoresis
- Microelectrophoretic
- Microhistochemically
- Microinterferometers
- Microinterferometric
- Micromineralogically
- Microminiaturisation
- Microminiaturization
- Micromorphologically
- Microneurosurgically
20 Letter Words Starting With N
- Nanolithographically
- Naphthalenesulphonic
- Nephroangiosclerosis
- Nephroureterectomies
- Neurochorioretinitis
- Neuroendocrinologies
- Neuroendocrinologist
- Neuropharmacological
- Neuropharmacologists
- Neurophysiologically
- Neuropsychiatrically
- Neuropsychologically
- Nonanachronistically
- Noncannibalistically
- Noncommunicativeness
- Noncontemporaneities
- Noncontemporaneously
- Nondenominationalism
- Nondestructivenesses
- Nondeterminativeness
- Nondeterministically
- Nondisqualifications
- Nonelectrochemically
- Nonimmunocompromised
- Noninstitutionalised
- Noninstitutionalized
- Noninterdisciplinary
20 Letter Words Starting With O
- Obstructionistically
- Olivopontocerebellar
- Onychoosteodysplasia
- Oophorhysterectomies
- Oophorosalpingectomy
- Operationalistically
- Ophthalmodiastimeter
- Ophthalmodynamometer
- Ophthalmostatometers
- Ophthalmothermometer
- Orthodichlorbenzenes
- Orthodichlorobenzene
- Osteochondrofibromas
- Osteochondrosarcomas
- Otorhinolaryngologic
- Overapprehensiveness
- Overdifferentiations
- Overeditorialization
- Overenthusiastically
- Overintellectualized
- Overintellectualizes
20 Letter Words Starting With P
- Pachycephalosauruses
- Palaeoanthropologist
- Palaeobiochemistries
- Palaeobiogeographers
- Palaeobiogeographies
- Palaeoceanographical
- Palaeoclimatological
- Palaeoclimatologists
- Palaeoethnographical
- Palaeoethnologically
- Palaeogeographically
- Palaeoherpetological
- Palaeoherpetologists
- Palaeohistologically
- Palaeohydrographical
- Palaeoichthyological
- Palaeoichthyologists
- Palaeolimnologically
- Palaeopathologically
- Palatopharyngoplasty
- Paleoanthropological
- Paleoanthropologists
- Paleobiogeographical
- Paleodendrologically
- Paleoentomologically
- Paleoenvironmentally
- Paleophysiographical
- Paleotempestologists
- Paleotypographically
- Pancreatectomisation
- Pancreatectomization
- Pancreatoenterostomy
- Papilloadenocystomas
- Paradichlorobenzenes
- Parallelogrammatical
- Parathyroidectomised
- Parathyroidectomises
- Parathyroidectomized
- Parathyroidectomizes
- Pathophysiologically
- Perhydrophenanthrene
- Pericardicperitoneal
- Pericardioperitoneal
- Phacoemulsifications
- Phaeochromocytoblast
- Pharmacoepidemiology
- Pharmacomechanically
- Phenanthrenequinones
- Phenylaceticaldehyde
- Phenylpropanolamines
- Phenylthiocarbamides
- Philoprogenitiveness
- Phoneticogrammatical
- Phonocardiographical
- Phosphatidylcholines
- Phosphatidylinositol
- Phosphoenolpyruvates
- Phosphoethanolamines
- Phosphofructokinases
- Phosphoglycoproteins
- Phosphomonoesterases
- Photoautotrophically
- Photocarcinogenicity
- Photochronographical
- Photodisintegrations
- Photoelectrocatalyse
- Photoelectrocatalyze
- Photofluorographical
- Photointerpretations
- Photophosphorylating
- Photophosphorylation
- Photophosphorylators
- Photopolymerisations
- Photoreconnaissances
- Polyvinylpyrrolidone
- Professionalizations
20 Letter Words Starting With R
- Radioimmunoassayable
- Radiopasteurizations
- Radiopharmaceuticals
- Radiotelegraphically
- Reconceptualisations
- Reconceptualizations
- Recontextualisations
- Recontextualizations
- Reendothelialisation
- Reendothelialization
- Reepithelialisations
- Reepithelializations
- Reindustrialisations
- Reindustrializations
- Reinstitutionalizing
- Reorthogonalisations
- Reorthogonalizations
20 Letter Words Starting With S
- Salpingooophorectomy
- Semiautobiographical
- Semiconservativeness
- Seminationalisations
- Seminationalizations
- Sesquipedaliophobics
- Sigmoidorectostomies
- Spectrocolourimeters
- Spectrocolourimetric
- Spectrofluorometrics
- Spectrofluorometries
- Spectroheliographies
- Spectrophotoelectric
- Spectrophotographers
- Spectrophotometrical
- Spectrophotometrists
- Spectroradiometrical
- Spectroradiometrists
- Sphingophospholipids
- Stereophotogrammetry
- Sternocleidomastoids
20 Letter Words Starting With T
- Tectonostratigrapher
- Tectonostratigraphic
- Tetrahydrocannabinol
- Tetrahydrocarbazoles
- Tetrahydropyrimidine
- Tetramethylbenzidine
- Tetranortriterpenoid
- Tetrapolymerisations
- Tetrapolymerizations
- Thermocauterisations
- Thermocauterizations
- Thermoelectronically
- Thermogeographically
- Thermometrographical
- Thermophosphorescent
- Thermopolymerisation
20 Letter Words Starting With U To X
- Ultracentrifugations
- Ultrafilterabilities
- Ultrafundamentalists
- Ultramicrochemically
- Ultramicroscopically
- Ultrapasteurizations
- Ultrarevolutionaries
- Ultrasegregationists
- Ultratraditionalists
- Uncharacteristically
- Uncompromisingnesses
- Unconscionablenesses
- Underaccomplishments
- Undercapitalisations
- Undercapitalizations
- Underclassifications
- Underdescriptiveness
- Underdifferentiating
- Underdifferentiation
- Undergeneralisations
- Undergeneralizations
- Undermasculinisation
- Undermasculinization
- Underrepresentations
- Unrepresentativeness
- Vaginoperineorrhaphy
- Vasoepididymostomies
- Videonystagmographic
- Xenotransplantations
Common 20 Letter Words With Meanings
Thirty of these reach print outside a laboratory: business reporting, medical notes, legal argument, science journalism. They are the ones worth knowing, and each is an ordinary idea wrapped in extra parts.
- Internationalization: the process of extending a business, standard, or product beyond one country.
- Institutionalization: the act of making a practice permanent inside an organisation, or of placing someone in long-term care.
- Compartmentalization: the habit of keeping parts of life or thought separate so that one does not affect another.
- Counterrevolutionary: someone who opposes a revolution and works to restore what came before it.
- Uncharacteristically: in a way that goes against how a person normally behaves.
- Overenthusiastically: with more eagerness than the situation calls for.
- Existentialistically: in the manner of existentialist philosophy, which treats personal choice as the source of meaning.
- Indistinguishability: the condition of two objects being impossible to tell apart.
- Unrepresentativeness: the failure of a sample or group to reflect the whole it represents.
- Interconnectednesses: the many ways in which separate parts depend on one another.
- Distinguishabilities: the degrees to which similar objects remain possible to tell apart.
- Forethoughtfulnesses: the habits of planning ahead and anticipating what a situation needs.
- Professionalizations: the processes by which occupations gain formal training, standards, and status.
- Departmentalizations: the divisions of an organisation into separate departments.
- Undercapitalizations: situations in which a business lacks the money it needs to operate safely.
- Counterdemonstration: a protest staged in direct opposition to another protest.
- Counterintelligences: the branches of security work devoted to blocking foreign spying.
- Deinstitutionalizing: moving people out of long-stay institutions and into community care.
- Microminiaturization: the shrinking of electronic components to an extremely small scale.
- Electroencephalogram: the printed record of the brain’s electrical activity, known as an EEG.
- Sternocleidomastoids: the paired neck muscles running from the skull to the collarbone that turn the head.
- Keratoconjunctivitis: inflammation of both the cornea and the membrane covering the eye.
- Glomerulonephritides: the several forms of inflammation affecting the kidney’s filtering units.
- Hypercholesterolemia: an abnormally high level of cholesterol in the blood.
- Hydrochlorothiazides: the diuretic tablets widely prescribed to lower blood pressure.
- Radiopharmaceuticals: drugs containing a radioactive element, used to image or treat disease.
- Acetylcholinesterase: the enzyme that clears the signalling chemical acetylcholine from a nerve junction.
- Tetrahydrocannabinol: the compound in cannabis responsible for its psychoactive effect, shortened to THC.
- Buckminsterfullerene: the football-shaped carbon molecule of 60 atoms, named after the architect Buckminster Fuller.
- Immunohistochemistry: the laboratory technique that uses antibodies to find specific proteins in tissue.
Long Words In Science And Medicine
Technical English builds a word by joining Greek and Latin parts end to end, and at 20 letters that method is doing nearly all the work. Electroencephalogram is three parts and no more: electricity, brain, written record.
| Part | Meaning | 20 letter example |
|---|---|---|
| electro- | Electricity | Electroencephalogram |
| photo- | Light | Photoreconnaissances |
| hydro- | Water | Hydrochlorothiazides |
| immuno- | Immune system | Immunohistochemistry |
| counter- | Against | Counterrevolutionary |
| -ectomy | Surgical removal | Ureteronephrectomies |
| -ology | Field of study | Pharmacoepidemiology |
| -graphy | Recording | Electrocorticography |
P leads the alphabet here for the same reason it leads at 18 and 19 letters: it opens the largest prefix families in scientific English, among them photo-, phospho-, palaeo-, and psycho-.
How To Break Down Long Words
A word of this length is three or four parts joined end to end, so the trick is finding the joins rather than reading letter by letter.
Internationalization: inter + national + ization. Between nations, turned into a process.
Counterrevolutionary: counter + revolution + ary. Against the revolution, turned into a describing word.
Electroencephalogram: electro + encephalo + gram. Electricity, brain, written record. Nothing here needs memorising once the three parts are separate.
Uncharacteristically: un + characteristic + ally. Strip the front and the back and an everyday word is left in the middle.
Read the ending last, because it tells you the part of speech: -ly makes an adverb, -ness and -ity make nouns, -ation names a process. Shorter words behave the same way, so 19 letter words and 18 letter words work well for practice, with one part fewer to separate.
Long Words In Scrabble And Crosswords
A Scrabble board measures 15 squares across, so a word this long cannot be laid down at all. The same limit applies to Words With Friends, and Wordle asks for five letters, so these words never enter play in any of the three.
Crosswords are the exception, and 20 letters is the length where that starts to matter. In an American paper the Sunday grid runs 21 squares across, which leaves exactly enough room for a 20 letter answer plus one black square. Across British cryptic grids, which stay at 15 squares, setters reach for phrases instead of single words when they need a long answer along the top.
Related:
FAQs
English holds around 600 of them, and a quarter are not new words at all but stretched forms of shorter ones: 82 end in -ically and 78 end in -ations, so the root underneath is a word you already know.
Two reach ordinary business and policy writing: internationalization and institutionalization. Of the medical ones, electroencephalogram is the most familiar, since most people meet it as the EEG on a hospital chart.
Because 18 letters stand between the opening i and the closing n. Software teams shortened it that way to avoid typing the whole thing, and the same trick produced l10n for localization and a11y for accessibility.
It is the compound in cannabis responsible for the psychoactive effect, almost always shortened to THC. At 20 letters it is the most searched word of this length by a wide margin.
A carbon molecule of 60 atoms arranged in a hollow sphere of pentagons and hexagons. Chemists named it after Buckminster Fuller, whose geodesic domes use the same geometry.
No. Four letters produce none at this length: J, W, Y and Z. Q manages only number names.
No. The board measures 15 squares in each direction, so the word will not fit whatever tiles you draw. A 21-square Sunday crossword grid is the only common word-game space wide enough to take one.
You May Also Like
