18 letter words, grouped by first letter
- absentmindednesses
 - accumulativenesses
 - adenocarcinomatous
 - advantageousnesses
 - aerothermodynamics
 - agammaglobulinemia
 - agammaglobulinemic
 - anagrammatizations
 - angiocardiographic
 - anthropocentricity
 - anthropomorphizing
 - antiadministration
 - anticholinesterase
 - anticommercialisms
 - anticounterfeiting
 - antidiscrimination
 - antiferromagnetism
 - antivivisectionist
 - appreciativenesses
 - apprehensivenesses
 - archaeoastronomies
 - astrophotographers
 - astrophotographies
 - australopithecines
 - autobiographically
 
- bacteriorhodopsins
 - biocompatibilities
 - biodegradabilities
 - biotransformations
 - bloodthirstinesses
 - bourgeoisification
 - bureaucratizations
 
- cantankerousnesses
 - characteristically
 - chemiluminescences
 - chlorofluorocarbon
 - chlortetracyclines
 - cholecystectomized
 - chromolithographed
 - chromolithographer
 - chromolithographic
 - claustrophobically
 - coccidioidomycoses
 - coccidioidomycosis
 - collectivistically
 - commensurabilities
 - commercializations
 - communicablenesses
 - companionabilities
 - compartmentalising
 - compartmentalizing
 - comprehensibleness
 - conceptualizations
 - congregationalisms
 - congregationalists
 - consequentialities
 - conservativenesses
 - constitutionalisms
 - constitutionalists
 - constitutionalized
 - constitutionalizes
 - constructivenesses
 - consubstantiations
 - contemptiblenesses
 - contemptuousnesses
 - contradistinctions
 - conversationalists
 - counteraccusations
 - counteradaptations
 - counteradvertising
 - counteraggressions
 - counterconventions
 - counterculturalism
 - counterdemonstrate
 - counterdeployments
 - countereducational
 - countergovernments
 - counterinfluencing
 - counterinstitution
 - counterintuitively
 - counterpetitioning
 - counterprogramming
 - counterpropagandas
 - counterquestioning
 - counterreformation
 - counterretaliation
 - counterrevolutions
 - counterstrategists
 - countersuggestions
 - creditworthinesses
 - curmudgeonlinesses
 
- deconstructionists
 - decriminalizations
 - dedifferentiations
 - dehydrochlorinases
 - dehydrochlorinated
 - dehydrochlorinates
 - deinstitutionalize
 - deliberativenesses
 - dematerializations
 - demythologizations
 - denationalizations
 - dendrochronologies
 - dendrochronologist
 - denominationalisms
 - deoxyribonucleases
 - depersonalizations
 - dephosphorylations
 - determinablenesses
 - dextroamphetamines
 - diastereoisomerism
 - diethylcarbamazine
 - diethylstilbestrol
 - dihydroergotamines
 - dimethylhydrazines
 - dimethyltryptamine
 - diphenylhydantoins
 - disagreeablenesses
 - disconnectednesses
 - disconsolatenesses
 - discontentednesses
 - discourteousnesses
 - discriminabilities
 - disenfranchisement
 - dishonorablenesses
 - disingenuousnesses
 - disintermediations
 - disproportionately
 - disproportionating
 - disproportionation
 - disputatiousnesses
 - disreputablenesses
 - distinguishability
 
- echocardiographers
 - echocardiographies
 - electrocardiograms
 - electrocardiograph
 - electrochemistries
 - electrocorticogram
 - electrodepositions
 - electrodesiccation
 - electrodynamometer
 - electroluminescent
 - electromyographies
 - electrooculography
 - electrophilicities
 - electrophoretogram
 - electrophotography
 - electrophysiologic
 - electroretinograms
 - electroretinograph
 - entrepreneurialism
 - epithelializations
 - establishmentarian
 - ethnomethodologies
 - ethnomethodologist
 - ethnomusicological
 - ethnomusicologists
 - evapotranspiration
 - exceptionabilities
 - expressionlessness
 - extemporaneousness
 - exterritorialities
 
- faintheartednesses
 - feeblemindednesses
 - ferroelectricities
 - forethoughtfulness
 - fractionalizations
 
- gastroenterologies
 - gastroenterologist
 - gedankenexperiment
 - generalizabilities
 - geochronologically
 - glomerulonephritis
 - glottochronologies
 - glycosaminoglycans
 - granulocytopoieses
 - granulocytopoiesis
 - greatheartednesses
 
- handcraftsmanships
 - heavyheartednesses
 - hemidemisemiquaver
 - hemoglobinopathies
 - histocompatibility
 - histophysiological
 - homoscedasticities
 - hydroelectricities
 - hydrometallurgical
 - hydrometallurgists
 - hydrometeorologies
 - hydrometeorologist
 - hydroxytryptamines
 - hyperalimentations
 - hypercoagulability
 - hyperconcentration
 - hyperconsciousness
 - hypercorrectnesses
 - hyperimmunizations
 - hypernationalistic
 - hyperpigmentations
 - hyperpolarizations
 - hyperrationalities
 - hypersensitiveness
 - hypersensitivities
 - hypersensitization
 - hypoparathyroidism
 - hypophysectomizing
 - hyposensitizations
 
- immeasurablenesses
 - immunocytochemical
 - immunodeficiencies
 - immunofluorescence
 - immunohematologies
 - immunohematologist
 - immunopathological
 - immunopathologists
 - immunoprecipitated
 - immunoprecipitates
 - immunoreactivities
 - immunosuppressants
 - immunosuppressions
 - imperceptivenesses
 - imperishablenesses
 - impermissibilities
 - impersonalizations
 - imperturbabilities
 - impracticabilities
 - inappreciativeness
 - inarticulatenesses
 - inauspiciousnesses
 - incombustibilities
 - incommensurability
 - incommodiousnesses
 - inconceivabilities
 - inconclusivenesses
 - inconsequentiality
 - inconsiderableness
 - inconsolablenesses
 - incontestabilities
 - inconvertibilities
 - incorrigiblenesses
 - incorruptibilities
 - indefatigabilities
 - indestructibleness
 - indiscriminateness
 - indiscriminatingly
 - indispensabilities
 - indisputablenesses
 - indissolublenesses
 - individualizations
 - industrializations
 - inexhaustibilities
 - inexplicablenesses
 - inexpressibilities
 - inexpressivenesses
 - inexpugnablenesses
 - inharmoniousnesses
 - inhospitablenesses
 - institutionalising
 - institutionalizing
 - insubstantialities
 - insufferablenesses
 - insusceptibilities
 - intellectualnesses
 - intelligiblenesses
 - interchangeability
 - intercolumniations
 - intercommunicating
 - intercommunication
 - interconnectedness
 - interinstitutional
 - intermediatenesses
 - interminablenesses
 - internationalising
 - internationalities
 - internationalizing
 - interoperabilities
 - interpretabilities
 - interrelatednesses
 - interrelationships
 - intersubstitutable
 - intransitivenesses
 - intraventricularly
 - introspectionistic
 - invulnerablenesses
 - irreconcilableness
 - irremediablenesses
 - irreplaceabilities
 - irrepressibilities
 - irreproachableness
 - irresistiblenesses
 - irresponsibilities
 - irresponsivenesses
 - irretrievabilities
 
- knowledgeabilities
 
- landlubberlinesses
 - largeheartednesses
 - latitudinarianisms
 - lepidopterological
 - lepidopterologists
 - lightheartednesses
 - lipopolysaccharide
 - lumpenproletariats
 - lymphangiographies
 
- macroglobulinemias
 - macrophotographies
 - magnetoresistances
 - magnetostrictively
 - maladministrations
 - malcontentednesses
 - manipulativenesses
 - mechanochemistries
 - melodramatizations
 - meretriciousnesses
 - metallographically
 - methemoglobinemias
 - methylcholanthrene
 - methylnaphthalenes
 - methylprednisolone
 - microcalorimetries
 - microcrystallinity
 - microdensitometers
 - microdensitometric
 - microencapsulating
 - microencapsulation
 - microenvironmental
 - microlepidopterous
 - micromanipulations
 - micrometeorologies
 - micrometeorologist
 - micromorphological
 - micropaleontologic
 - microphotographers
 - microphotographies
 - microradiographies
 - microreproductions
 - mineralocorticoids
 - misadministrations
 - misclassifications
 - misidentifications
 - misinterpretations
 - misrepresentations
 - monochromaticities
 - mucopolysaccharide
 - muddleheadednesses
 - multicellularities
 - multifariousnesses
 - myeloproliferative
 
- neuroendocrinology
 - neuropharmacologic
 - neurophysiological
 - neurophysiologists
 - neuropsychiatrists
 - neuropsychological
 - neuropsychologists
 - neurotransmissions
 - nonanthropological
 - nonanthropologists
 - nonarbitrarinesses
 - noncommutativities
 - noncomparabilities
 - nonconfrontational
 - noncooperationists
 - nondeductibilities
 - nondestructiveness
 - nondiscriminations
 - nonfraternizations
 - noninterchangeable
 - noninterventionist
 - nonrepresentatives
 - nonrevolutionaries
 
- obstreperousnesses
 - ophthalmologically
 - opinionativenesses
 - organophosphoruses
 - orthogonalizations
 - orthopsychiatrists
 - oscillographically
 - ostentatiousnesses
 - otherworldlinesses
 - overcapitalization
 - overcentralization
 - overclassification
 - overcommercialized
 - overcommercializes
 - overcommunications
 - overconcentrations
 - overembellishments
 - overextrapolations
 - overfertilizations
 - overgeneralization
 - overidentification
 - overindebtednesses
 - overindustrialized
 - overindustrializes
 - overinterpretation
 - overoptimistically
 - overprotectiveness
 - overrepresentation
 - oversimplification
 - overspecialization
 - ovolactovegetarian
 
- paleoclimatologies
 - paleoclimatologist
 - particularizations
 - pathophysiological
 - pentachlorophenols
 - pentylenetetrazols
 - perchloroethylenes
 - perpendicularities
 - pertinaciousnesses
 - phenomenologically
 - pheochromocytomata
 - phonocardiographic
 - phosphodiesterases
 - phosphoglucomutase
 - photodecomposition
 - photodisintegrated
 - photodisintegrates
 - photodissociations
 - photolithographies
 - photolithographing
 - photomicrographies
 - photomorphogeneses
 - photomorphogenesis
 - photoreactivations
 - photoreproductions
 - photosensitivities
 - photosensitization
 - photosynthetically
 - physiopathological
 - phytohemagglutinin
 - piezoelectricities
 - polyacrylonitriles
 - polychromatophilia
 - polychromatophilic
 - polyesterification
 - polymorphonuclears
 - polyribonucleotide
 - postmillenarianism
 - postmillennialisms
 - postmillennialists
 - postpsychoanalytic
 - praiseworthinesses
 - predestinarianisms
 - premillenarianisms
 - preposterousnesses
 - presumptuousnesses
 - proletarianization
 - pronounceabilities
 - propagandistically
 - propertylessnesses
 - provincializations
 - pseudonymousnesses
 - pseudoparenchymata
 - pseudotuberculoses
 - pseudotuberculosis
 - psychoanalytically
 - psychobiographical
 - psychopathological
 - psychopathologists
 - psychopharmacology
 - psychophysiologies
 - psychophysiologist
 - puzzleheadednesses
 
- quantificationally
 - quantitativenesses
 - quasiperiodicities
 - quattuordecillions
 - questionablenesses
 
- radiochromatograms
 - radiosensitivities
 - rambunctiousnesses
 - rechromatographies
 - rechromatographing
 - reconstructionisms
 - reconstructionists
 - recrystallizations
 - redistributionists
 - rehospitalizations
 - reinstitutionalize
 - remunerativenesses
 - renationalizations
 - reprehensibilities
 - representationally
 - representativeness
 - representativities
 - revascularizations
 - rhabdomyosarcomata
 - ribonucleoproteins
 - roentgenologically
 
- sacrilegiousnesses
 - satisfactorinesses
 - sedimentologically
 - semiconservatively
 - semidomestications
 - semipermeabilities
 - semiprofessionally
 - semiquantitatively
 - sentimentalization
 - shortsightednesses
 - simplemindednesses
 - simultaneousnesses
 - sociopsychological
 - somnambulistically
 - soporiferousnesses
 - spectrofluorimeter
 - spectrofluorometer
 - spectrofluorometry
 - spectrographically
 - spectroheliographs
 - spectroheliography
 - spectrohelioscopes
 - spectrophotometers
 - spectrophotometric
 - sphygmomanometries
 - stereophotographic
 - stereoregularities
 - stereospecifically
 - stoichiometrically
 - stoutheartednesses
 - structuralizations
 - subcategorizations
 - subclassifications
 - subconsciousnesses
 - submicroscopically
 - substitutabilities
 - superadministrator
 - superciliousnesses
 - supercivilizations
 - superconglomerates
 - superintellectuals
 - superintelligences
 - superminicomputers
 - supernaturalnesses
 - supersensitivities
 - supersophisticated
 - supranationalities
 
- tachistoscopically
 - telecommunications
 - territorialization
 - theatricalizations
 - thermoluminescence
 - thermoplasticities
 - thrombophlebitides
 - transcendentalisms
 - transcendentalists
 - transformationally
 - transilluminations
 - transistorizations
 - transmissibilities
 - transmogrification
 - transportabilities
 - transubstantiating
 - transubstantiation
 - triboelectricities
 - triboluminescences
 - trichloroethylenes
 - triskaidekaphobias
 
- ultracentrifugally
 - ultraconservatisms
 - ultraconservatives
 - ultramicroscopical
 - ultranationalistic
 - ultrarevolutionary
 - ultrasophisticated
 - unaccountabilities
 - unassailablenesses
 - unattractivenesses
 - unchangeablenesses
 - uncharitablenesses
 - uncompromisingness
 - unconscionableness
 - unconstitutionally
 - unconvincingnesses
 - unenthusiastically
 - ungrammaticalities
 - uniformitarianisms
 - unintelligibleness
 - unpredictabilities
 - unprinciplednesses
 - unprofitablenesses
 - unreasonablenesses
 - unresponsivenesses
 - unrestrainednesses
 - unsatisfactoriness
 - unscrupulousnesses
 - unseasonablenesses
 - unsubstantialities
 
- vaingloriousnesses
 - valetudinarianisms
 - verisimilitudinous
 - videoconferencings
 
- weatherproofnesses