3 syllables:
jealously

5 syllables:
overzealously

2 syllables:
thessaly

3 syllables:
severally, splendidly, pleasantly, messily, tendency, ebony, pedigree, credibly, gemini, venally, threepenny, leprosy, prelacy, lengthily, elegy, readily, secrecy, tenantry, weaponry, helplessly, equity, penally, recently, zestfully, ceaselessly, remedy, breathlessly, brevity, evenly, revelry, flexibly, melody, steadily, entity, sneakily, equally, genially, jealousy, restfully, enemy, seventy, entropy, tensity, peasantry, clemency, peaceably, velvety, evilly, decently, threnody, sensibly, gleefully, devilry, chemistry, pedantry, pregnancy, legacy, bestially, cecity, necropsy, greedily, sesame, chieftaincy, zealotry, mentally, density, dreadfully, helpfully, vis-a-vis, regency, testily, speedily, specially, embassy, dreamily, tenancy, pleasantry, centrally, easily, leniency, frequency, kennedy, deputy, lemony, secondly, enmity, legatee, decency, felony, peacefully, preciously, leniently, legally, recipe, ecstasy, especially, debauchee, specialty, presently, destiny, heavily, heavenly, medically, endlessly, empathy, chemically, penalty, frequently, benghazi, dextrously, ectropy, emigree, fecklessly, jejunely, legibly, lenity, melanie, pebbly, pederasty, resiny, self-pity, selflessly, senselessly, sentiency, stephanie, tepidly, trenchancy, trepidly, vengefully, yemeni, zestily, ceiba tree, cheekily, creakily, dreamfully, heedfully, heedlessly, needfully, piquancy, piquantly, readably, recency, screakily, seamanly, wheezily

4 syllables:
deceitfully, theosophy, incessantly, rebelliously, transcendency, detestably, acceptably, conveniently, resplendently, extremity, ascendancy, nonentity, mastectomy, expectancy, identity, necessity, dependably, treacherously, lamentably, successfully, inequity, discrepancy, sequentially, unsteadily, lobectomy, ascendency, preferably, serenity, fidelity, unpleasantly, nephrectomy, potentially, high frequency, death penalty, tremendously, indecency, essentially, flux density, desperately, schenectady, lumpectomy, intrepidly, ostensibly, sententiously, complexity, splenectomy, infrequency, insensibly, telemetry, respectfully, respectably, hegemony, generally, inflexibly, unequally, dependency, supremacy, anemone, longevity, infrequently, repentantly, facetiously, ineffably, perplexity, vasectomy, obscenely, low frequency, resplendency, solemnity, contemptuously, amenity, federally, unspeakably, intensity, relevantly, heredity, uneasily, perceptibly, convexity, incredibly, integrity, unevenly, obesity, allegedly, indemnity, vehemently, incessancy, conceivably, separately, telepathy, illegally, licentiously, low density, regrettably, thrombectomy, tentatively, infectiously, penelope, acephaly, confessedly, defencelessly, domenici, forelady, illegibly, immensity, impendency, impetuously, inclemency, jack kennedy, lieutenancy, neurectomy, perplexedly, polemically, pretentiously, professedly, quiescency, refreshfully, relentlessly, revengefully, shell entity, unhelpfully, vulvectomy, with empathy, archdeaconry, believably, benignancy, benignantly, benignity, conceitedly, indecently, most recently, pass easily, serigraphy, unreadably

5 syllables:
tonsillectomy, orchidectomy, geochemistry, mask of pregnancy, obediently, hysterectomy, eventually, sympathectomy, life expectancy, sentimentally, exceptionally, consequentially, confederacy, biochemistry, accidentally, mastoidectomy, independently, tubal pregnancy, reverentially, oophorectomy, white supremacy, professionally, stapedectomy, orchiectomy, pneumonectomy, salpingectomy, unbelievably, thyroidectomy, disrespectfully, appendectomy, penitentially, irreverently, macrencephaly, abstemiously, rhytidectomy, incidentally, intemperately, open sesame, providentially, high fidelity, prostatectomy, unacceptably, deferentially, photochemistry, independency, conscientiously, embolectomy, microcephaly, fundamentally, vapor density, anencephaly, reprehensibly, unsuccessfully, acrocephaly, change integrity, change intensity, clinocephaly, coalescency, create mentally, detrimentally, drunken revelry, field intensity, half-intensity, high-fidelity, hydrocephaly, intumescency, laminectomy, laryngectomy, line of destiny, macrocephaly, megacephaly, meniscectomy, mortal enemy, mountain ebony, nanocephaly, naval weaponry, of necessity, scaphocephaly, school of dentistry, sigmoidectomy, unforgettably, unpretentiously, unrepentantly, acromegaly, antecedently, contumeliously, inconveniently, self-conceitedly, unachievably, unimpeachably

6 syllables:
cholecystectomy, unconventionally, coincidentally, biogeography, unintentionally, ovariectomy, environmentally, medium frequency, radio frequency, radiochemistry, physical chemistry, simple mastectomy, impetuosity, manifest destiny, audio frequency, cardiomegaly, interdependency, relative frequency, electrochemistry, organic chemistry, cercopithecidae, experimentally, cosmetic dentistry, inconsequentially, very high frequency, very low frequency, adrenalectomy, immunochemistry, relative density, adenoidectomy, anas penelope, appendicectomy, change of integrity, genus penelope, militant tendency, panhysterectomy, pedal extremity, unsentimentally, absolute frequency, infrared frequency

7 syllables:
extremely low frequency, ovarian pregnancy, radical mastectomy, inorganic chemistry, fundamental frequency, extremely high frequency, magnetic flux density, paleogeography, abdominal pregnancy, total hysterectomy, department of chemistry, executive clemency, feeling of identity, john fitzgerald kennedy, magnetic intensity, suprarenalectomy

8 syllables:
radical hysterectomy, conformational entropy, interpersonal chemistry

10 syllables:
modified radical mastectomy