5 letters:
otomy

7 letters:
axotomy, myotomy, ototomy, peotomy, scotomy, zootomy

8 letters:
aplotomy, celotomy, colotomy, ileotomy, kelotomy, labotomy, menotomy, oncotomy, onkotomy, tenotomy, vagotomy, venotomy, xylotomy

9 letters:
adenotomy, androtomy, aortotomy, celiotomy, cirsotomy, colpotomy, coniotomy, cordotomy, costotomy, cricotomy, culdotomy, cyclotomy, cystotomy, dichotomy, frenotomy, goniotomy, hippotomy, histotomy, iridotomy, leucotomy, leukotomy, lithotomy, mammotomy, mastotomy, meatotomy, necrotomy, neurotomy, orchotomy, orthotomy, phytotomy, pubiotomy, pulpotomy, rhinotomy, tarsotomy, tendotomy, thyrotomy, uterotomy, valvotomy

10 letters:
angeiotomy, arthrotomy, atticotomy, blastotomy, canthotomy, cardiotomy, chordotomy, craniotomy, dichotomie, embryotomy, enterotomy, entomotomy, fasciotomy, glossotomy, hepatotomy, herniotomy, hymenotomy, jejunotomy, keratotomy, laminotomy, laparotomy, nephrotomy, onychotomy, orbitotomy, ovariotomy, pelviotomy, phlebotomy, plasmotomy, pleurotomy, pneumotomy, pogonotomy, proctotomy, pylorotomy, rachiotomy, radicotomy, rumenotomy, sclerotomy, sinusotomy, splenotomy, sternotomy, strabotomy, tractotomy, trichotomy, vaginotomy, varicotomy, ventrotomy, vesicotomy

11 letters:
achillotomy, adhesiotomy, alveolotomy, arteriotomy, bronchotomy, callosotomy, capsulotomy, cephalotomy, chondrotomy, cingulotomy, condylotomy, duodenotomy, escharotomy, fistulotomy, herpetotomy, hippopotami, hysterotomy, ichthyotomy, lacrimotomy, laryngotomy, myotenotomy, myringotomy, omphalotomy, orchidotomy, ornithotomy, pallidotomy, perineotomy, polychotomy, syringotomy, thalamotomy, thoracotomy, tonsilotomy, tracheotomy, ureterotomy, urethrotomy, valvulotomy

12 letters:
amygdalotomy, anthropotomy, aponeurotomy, blepharotomy, esophagotomy, foraminotomy, ossiculotomy, pharyngotomy, pneumonotomy, prostatotomy, salpingotomy, sigmoidotomy, staphylotomy, subdichotomy, syndesmotomy, thyroidotomy, tonsillotomy, trachelotomy

13 letters:
encephalotomy, pancreatotomy, pottawattomie, pyloromyotomy, splanchnotomy, stricturotomy, symphyseotomy, symphysiotomy, vestibulotomy

14 letters:
cholecystotomy, choledochotomy, cholelithotomy, commissurotomy, cricothyrotomy, cystolithotomy, lymphangiotomy, mediastinotomy, minilaparotomy, pericardiotomy, pyelolithotomy, sphincterotomy, synchondrotomy, ultramicrotomy, ventriculotomy

15 letters:
achillotenotomy, dacryocystotomy, nephrolithotomy

16 letters:
gastroelytrotomy

17 letters:
cricothyroidotomy, gastrohysterotomy

18 letters:
laryngotracheotomy

19 letters:
abdominohysterotomy, choledocholithotomy

5 letters:
ology

6 letters:
colony, policy, bodily, sodomy, botany, homily, comedy, romany, polony, monody, wobbly, polity, oddity, albany

7 letters:
wallaby, volubly, modesty, wannabe, zoology, novelty, economy, ecology, prodigy, boloney, honesty, geology, geodesy, audibly, quality, ptolemy, solidly, dovekie, neology, apology, progeny, gossipy, prosody, odyssey, otology, urology, anomaly, biology, enology, conakry, awfully, balsamy, falsity, gaudily, myology, paucity, saucily

8 letters:
ontogeny, monotony, autonomy, pomology, broccoli, synonymy, possibly, rocketry, sinology, horology, mycology, misogamy, aerology, oncology, geometry, quantity, homogeny, monopoly, doxology, tocology, psalmody, cytology, ontology, axiology, twopenny, nosology, penology, atrocity, velocity, frostily, misology, agrology, honestly, etiology, apostasy, ideology, hostelry, moronity, bonhomie, equality, oenology, porosity, commonly, potbelly, potently, theology, virology, wantonly, jocosity, ethology, modestly, serology, colloquy, mahogany, monandry, cobwebby, agronomy, prophecy, probably, ferocity, posology, wannabee, idolatry, homology, monogamy, doggedly, laudably, lawfully, metonymy, rheology, solemnly, solvency, tawdrily, topology

9 letters:
monopsony, sinuosity, comradely, hostilely, cacophony, astronomy, aetiology, verbosity, angiology, colostomy, etymology, frivolity, uranology, garbology, hagiology, neurology, philology, democracy, radiology, anthology, comradery, phonology, phytology, hypocrisy, ethnology, loquacity, adiposity, viscosity, dobsonfly, commodity, gibbosity, teleology, impotency, pathology, paleology, constancy, audiology, genealogy, sociology, poenology, crotchety, animosity, allopathy, theocracy, curiosity, phylogeny, tautology, optometry, contrasty, callosity, histology, hydrology, geography, mythology, allometry, biography, astrology, anisogamy, autocracy, precocity, petrology, limnology, androgyny, cosmology, inaudibly, lawlessly, necrology, plausibly, raucously, scatology

10 letters:
hematology, archeology, anemometry, toxicology, psephology, technology, topography, conchology, physiology, teratology, demography, mineralogy, apostrophe, audiometry, impolitely, inequality, embryology, gastronomy, typography, parisology, tortuosity, improbably, constantly, impossibly, tuberosity, comparably, proctology, egyptology, mediocrity, prodigally, philosophy, dishonesty, speleology, ideography, conjugally, generosity, cardiology, psychology, insolvency, entomology, immunology, hydrometry, morphology, adenopathy, lexicology, astrometry, sociometry, chronology, numerosity, phrenology, low comedy, holography, seismology, gynecology, cautiously, flawlessly, hydropathy, unlawfully, wrongfully

11 letters:
laparoscopy, actinometry, eschatology, dermatology, volcanology, sovereignty, lithography, monstrously, haematology, pornography, thermometry, primatology, orthography, scientology, paleobotany, ichthyology, herpetology, gynaecology, religiosity, stereoscopy, jejunostomy, aristocracy, meteorology, inconstancy, radiography, methodology, bureaucracy, planography, photography, terminology, cartography, monstrosity, archaeology, consciously, mammography, ethnography, criminology, ornithology, climatology, anemography, hagiography, despondency, gerontology, responsibly, fluoroscopy, grandiosity, angiography, allergology, dauntlessly, dishonestly, fossilology, homoeopathy, implausibly, meritocracy, vulcanology

12 letters:
macrocephaly, antimonopoly, cardiography, bacteriology, rheumatology, anthropology, true anomaly, bibliography, lexicography, epidemiology, demonstrably, trade policy, paleobiology, trigonometry, despondently, spectroscopy, choreography, epistemology, oceanography, neurobiology, tracheostomy, paleontology, meniscectomy, pharmacology, microbiology, densitometry, spectrometry, incautiously, thoughtfully

13 letters:
token economy, autobiography, ophthalmology, endocrinology, fiscal policy, human ecology, geomorphology, biotechnology, unconsciously, palaeontology, arteriography, irresponsibly, numismatology, anthropometry, anorthography, cross-country, inexhaustibly, thoughtlessly

14 letters:
cardiomyopathy, market economy, solid geometry, anesthesiology, musical comedy, paleopathology, bioclimatology, foreign policy, folk etymology, cinematography, parapsychology, plane geometry, chromatography, otolaryngology

15 letters:
psychopathology, radio astronomy, ultrasonography, escape velocity, roentgenography, high technology, crystallography, neuropsychology, telephotography, paleornithology, neurophysiology, immunopathology, muzzle velocity

16 letters:
natural theology, situation comedy, child psychology, social democracy, depth psychology, paleoclimatology, african mahogany, psychophysiology, glottochronology, electromyography, insurance policy, moral philosophy, hemoglobinopathy

17 letters:
micropaleontology, social psychology, terminal velocity, molecular biology, chromolithography, dynamic viscosity, dialect geography, paleoanthropology, analytic geometry, political economy, haemoglobinopathy

18 letters:
psychopharmacology, congenital anomaly, physical geography, economic geography, spherical geometry, proprietary colony, offset lithography, applied psychology, natural philosophy

19 letters:
projective geometry, clinical psychology, philippine mahogany, hyperbolic geometry, social anthropology

20 letters:
paper chromatography, cognitive psychology, doctor of philosophy

21 letters:
cultural anthropology, physical anthropology, industrial psychology, column chromatography

22 letters:
comparative psychology

23 letters:
experimental psychology

24 letters:
physiological psychology, coefficient of viscosity, developmental psychology