3 syllables:
myologists

4 syllables:
apologists, astrologists, biologists, chronologists, cosmologists, cryptologists, cytologists, ecologists, ethnologists, ethologists, geologists, graphologists, histologists, horologists, hydrologists, ichthyologists, limnologists, mixologists, monologists, morphologists, mycologists, mythologists, necrologists, nephrologists, neurologists, oncologists, ontologists, otologists, pathologists, pedologists, penologists, philologists, phrenologists, phycologists, proctologists, psephologists, psychologists, scatologists, seismologists, serologists, sexologists, sinologists, tautologists, technologists, topologists, urologists, virologists, zoologists

5 syllables:
acarologists, anthropologists, archaeologists, archeologists, audiologists, campanologists, cardiologists, climatologists, cosmetologists, craniologists, creatologists, criminologists, demonologists, deontologists, dermatologists, embryologists, entomologists, escapologists, eschatologists, etymologists, futurologists, genealogists, gerontologists, glaciologists, gynaecologists, gynecologists, haematologists, hematologists, herpetologists, ideologists, immunologists, kremlinologists, laryngologists, malacologists, mineralogists, musicologists, numerologists, odontologists, oenologists, ophthalmologists, ornithologists, osteologists, pharmacologists, physiologists, radiologists, reflexologists, rheumatologists, scientologists, semiologists, sociologists, speleologists, teratologists, toxicologists, vexillologists, volcanologists, vulcanologists

6 syllables:
bacteriologists, biotechnologists, cryobiologists, cryptozoologists, endocrinologist's, endocrinologists, epistemologists, kinesiologists, meteorologist's, meteorologists, microbiologists, neonatologists, neurobiologists, neuropsychologists, paleontologists, parapsychologists, parasitologists, phenomenologists, psychobiologists, sovietologists, venereologists

7 syllables:
anaesthesiologists, anesthesiologists, epidemiologists, ethnomusicologists, gastroenterologists, otolaryngologists, psychopharmacologists, radiobiologists

9 syllables:
otorhinolaryngologists

3 syllables:
bottomless, cognizance, columnists, commonness, communists, confidence, conscienceless, consciousness, consequence, consonance, continence, continents, documents, dominance, godlessness, honestness, modestness, monuments, noxiousness, obstinance, occupants, oculus, ominous, omnibus, omphalus, onymous, opulence, oxalis, pompousness, populace, populous, populus, profitless, prominence, prophetess, protestants, provenance, providence, romulus, rottenness, scolytus, slothfulness, somnolence, spotlessness, squalidness, stolidness, strophanthus, vomitus, watchfulness

4 syllables:
abdominous, acrogenous, acromphalus, acropolis, ammotragus, androgenous, anonymous, anthophagous, apogamous, apophasis, astomatous, autogenous, autologous, autolysis, autonomous, carpophagous, cryptogamous, cytolysis, endogamous, eponymous, esophagus, exogamous, gymnopilus, hippotragus, homologous, hydrolysis, hypothesis, idolatress, improvidence, incompetence, incontinence, lose consciousness, melophagus, metropolis, monogamous, monotonous, necropolis, nitrogenous, obnoxiousness, oesophagus, panonychus, phytophagous, predominance, recognizance, reconnaissance, saprophagous, sarcolemnous, sarcophagus, self-confidence, self-consciousness, subconsciousness, synonymous, taurotragus, uncommonness, uropsilus, with confidence, zoophagous

5 syllables:
acantholysis, air reconnaissance, amylolysis, anisogamous, anthropophagus, campylotropous, creeping oxalis, disconsolateness, electrolysis, entomophilous, fibrinolysis, genus oxalis, haematolysis, hematolysis, heterologous, hippopotamus, loss of consciousness, megalopolis, nonautonomous, nonnitrogenous, ophiophagus, proteolysis, semiconsciousness, stephanopoulos, stream of consciousness, unselfconsciousness, vote of confidence

6 syllables:
adrianopolis, bacteriolysis, bacteriophagous, megalobatrachus

7 syllables:
displaying incompetence, genus hippopotamus

8 syllables:
alcoholics anonymous, electronic reconnaissance, urinary incontinence

15 syllables:
international society for krishna consciousness