3 syllables:
density, tensity

4 syllables:
dimensity, extensity, flux density, high-density, immensity, intensity, low-density, low density, perpensity, propensity, protensity

5 syllables:
change intensity, double-density, field intensity, half-intensity, vapor density

6 syllables:
hyperintensity, radiodensity, relative density

7 syllables:
magnetic flux density, magnetic intensity

3 syllables:
benghazi, bestially, breathlessly, brevity, centrally, chemically, chemistry, clemency, credibly, deputy, desperately, destiny, devilry, dextrously, dreadfully, ebony, ecstasy, ectropy, elegy, embassy, emigree, empathy, endlessly, enemy, enmity, entity, entropy, equity, evilly, fecklessly, federally, felony, flexibly, gemini, generally, heavenly, heavily, helpfully, helplessly, jealously, jealousy, jejunely, kennedy, legacy, legatee, legibly, lemony, lengthily, lenity, leprosy, medically, melanie, melody, mentally, peasantry, pebbly, pedantry, pederasty, pedigree, penally, penalty, pleasantly, pleasantry, preciously, preferably, pregnancy, presently, readily, recipe, remedy, resiny, restfully, revelry, secondly, self-pity, selflessly, senselessly, sensibly, sentiency, separately, sesame, seventy, severally, specially, specialty, splendidly, steadily, stephanie, tenancy, tenantry, tendency, tentatively, tepidly, testily, threnody, trenchancy, trepidly, velvety, venally, vengefully, weaponry, yemeni, zealotry, zestfully, zestily

4 syllables:
acceptably, acephaly, allegedly, amenity, anemone, ascendancy, ascendency, complexity, confederacy, confessedly, contemptuously, convexity, death penalty, defencelessly, dependency, detestably, discrepancy, domenici, especially, essentially, eventually, exceptionally, expectancy, extremity, fidelity, forelady, hegemony, heredity, identity, illegibly, impendency, impetuously, incessancy, incessantly, inclemency, incredibly, indemnity, ineffably, inequity, infectiously, inflexibly, insensibly, integrity, intrepidly, jack kennedy, lamentably, licentiously, lieutenancy, lobectomy, longevity, lumpectomy, mastectomy, necessity, nephrectomy, neurectomy, nonentity, ostensibly, penelope, perceptibly, perplexedly, perplexity, polemically, potentially, pretentiously, professedly, professionally, quiescency, rebelliously, refreshfully, regrettably, relentlessly, repentantly, respectably, respectfully, resplendency, resplendently, revengefully, schenectady, sententiously, sequentially, serenity, shell entity, solemnity, splenectomy, successfully, supremacy, telemetry, telepathy, thrombectomy, transcendency, tremendously, unhelpfully, unpleasantly, unsteadily, vasectomy, vulvectomy, with empathy

5 syllables:
accidentally, acrocephaly, anencephaly, appendectomy, biochemistry, change integrity, clinocephaly, coalescency, conscientiously, consequentially, create mentally, deferentially, detrimentally, disrespectfully, drunken revelry, embolectomy, fundamentally, geochemistry, high-fidelity, high fidelity, hydrocephaly, hysterectomy, incidentally, independency, independently, intumescency, laminectomy, laryngectomy, life expectancy, line of destiny, macrocephaly, mask of pregnancy, mastoidectomy, megacephaly, meniscectomy, microcephaly, mortal enemy, mountain ebony, nanocephaly, naval weaponry, of necessity, oophorectomy, open sesame, orchidectomy, orchiectomy, penitentially, photochemistry, pneumonectomy, prostatectomy, providentially, reprehensibly, reverentially, rhytidectomy, salpingectomy, scaphocephaly, school of dentistry, sentimentally, sigmoidectomy, stapedectomy, sympathectomy, thyroidectomy, tonsillectomy, tubal pregnancy, unacceptably, unforgettably, unintentionally, unpretentiously, unrepentantly, unsuccessfully, white supremacy

6 syllables:
adenoidectomy, adrenalectomy, anas penelope, appendicectomy, change of integrity, cholecystectomy, coincidentally, cosmetic dentistry, electrochemistry, environmentally, experimentally, genus penelope, immunochemistry, inconsequentially, interdependency, manifest destiny, militant tendency, organic chemistry, ovariectomy, panhysterectomy, pedal extremity, physical chemistry, radiochemistry, simple mastectomy, unsentimentally

7 syllables:
abdominal pregnancy, department of chemistry, executive clemency, feeling of identity, inorganic chemistry, john fitzgerald kennedy, ovarian pregnancy, radical mastectomy, suprarenalectomy, total hysterectomy

8 syllables:
conformational entropy, interpersonal chemistry, radical hysterectomy

10 syllables:
modified radical mastectomy