3 syllables:
quiddity

4 syllables:
acidity, acridity, algidity, aridity, avidity, calidity, callidity, cupidity, fervidity, fixidity, flaccidity, floridity, fulgidity, fumidity, gelidity, gravidity, hispidity, humidity, lanquidity, limpidity, liquidity, lividity, lucidity, marcidity, morbidity, pallidity, pavidity, pinguidity, placidity, prigidity, putidity, rabidity, rancidity, rapidity, rigidity, sapidity, solidity, squalidity, stolidity, stupidity, tepidity, timidity, torpidity, trepidity, tumidity, turbidity, validity, vapidity, vastidity, viridity, viscidity, vividity

5 syllables:
anacidity, comorbidity, illiquidity, insolidity, invalidity, pellucidity, subacidity, with validity

6 syllables:
hyperacidity, hypoacidity, pseudorapidity, semiaridity, semifluidity, semiliquidity, superacidity, superfluidity

7 syllables:
relative humidity, semipellucidity

3 syllables:
skillfully, visibly, timpani, symphony, synchrony, visually, tiffany, tinselly, whiffletree, infamy, flippancy, stringency, sympathy, viciously, wicopy, timothy, willowy, stickily, dimity, dittany, signally, wiggly, ministry, fixity, fidgety, instantly, vividly, filigree, brilliancy, litany, spitefully, symmetry, trilogy, brilliantly, stingily, finicky, trinity, brittany, imagery, instancy, villainy, bigotry, dismally, industry, fiscally, wilfully, flippantly, bigamy, dingily, mistily, rickety, dignity, willfully, tripoli, whippletree, differently, finitely, timidly, minutely, sicily, swingletree, infancy, piquancy, italy, syncope, chivalry, infantry, giddily, dizzily, bishopry, chintzily, filthily, flindosy, frigidly, hymnody, licitly, lingually, millime, minstrelsy, pipal tree, prissily, quizzically, ribbony, shittah tree, simile, skilfully, stringently, trickily, twinkly, viscidly, windily, winsomely, wriggly

4 syllables:
polygyny, proclivity, sufficiently, futility, magistracy, benignancy, proficiency, facsimile, hostility, captivity, vicinity, gravimetry, indignity, salinity, antiquity, malignancy, publicity, invisibly, contingency, auspiciously, virility, utility, implicitly, resiliency, obstinately, perniciously, astringency, toxicity, fragility, civility, antistrophe, ambitiously, affinity, antipathy, deficiency, spasticity, officially, cyclicity, initially, fertility, complicity, delinquency, sweet cicely, asynchrony, polyphony, senility, deliciously, infinity, epiphany, soliloquy, docility, ability, simplicity, religiously, abysmally, pasigraphy, miserably, polygamy, proximity, growth industry, felicity, antigone, sufficiency, explicitly, festivity, literally, activity, immorally, consistently, liberally, tonicity, mobility, prolixity, amphictyony, sphericity, culicidae, agility, somniloquy, nobility, ductility, asymmetry, consistency, propitiously, efficiency, debility, divinity, nativity, epitome, efficiently, calligraphy, exigency, irritably, acclivity, arms industry, blessed trinity, coal industry, declivity, film industry, forgivably, insistency, malignity, mendicancy, motivity, oil industry, permissibly, persistency, persnickety, plasticity, propinquity, put differently, rusticity, sanguinity, shoe industry, sign industry, steel industry, tactility, toy industry, unthinkably, ventriloquy, with sympathy

5 syllables:
intermittency, self-sufficiency, cucurbitaceae, alkalimetry, expeditiously, inauspiciously, exiguity, insufficiency, contractility, eccentricity, insufficiently, conditionally, relativity, creativity, unofficially, alkalinity, surreptitiously, masculinity, meretriciously, inefficiency, atonicity, originally, probability, supersymmetry, elasticity, domesticity, artificially, conductivity, injudiciously, volatility, holy trinity, deliberately, magnanimity, ellipticity, legibility, negativity, versatility, infelicity, peripherally, catholicity, additionally, electricity, femininity, inutility, calorimetry, feasibility, aborigine, inconsistency, chromaticity, unanimity, promiscuously, viability, fortuitously, traditionally, service industry, flexibility, possibility, productivity, irresistibly, inefficiently, unchristianly, specificity, avariciously, reactivity, colorimetry, capability, selectivity, absorptivity, banking industry, chondrodystrophy, concentricity, consanguinity, expansivity, fashion industry, granadilla tree, housing industry, imbecility, impermissibly, inconsistently, inhospitably, lighting industry, mass deficiency, mental imagery, mirror symmetry, movie industry, mutability, notability, perceptivity, plastics industry, progressivity, quotability, reflectivity, refractivity, reluctivity, resistivity, retentivity, risibility, sapodilla tree, sex activity, stretchability, syllabicity, tangibility, taoist trinity, transitivity, trucking industry, unambitiously, unforgivably, unpredictably, unpropitiously, without sympathy, with efficiency, with hostility, zinc deficiency

6 syllables:
compatibility, radial symmetry, idiosyncrasy, invisibility, superciliously, susceptibility, reliability, individually, amiability, unequivocally, periodicity, muscular dystrophy, availability, chemical industry, malleability, apocynaceae, perfectibility, joint probability, acceptability, mental deficiency, neuropsychiatry, responsibility, public utility, applicability, pusillanimity, irritability, adaptability, palatability, unconditionally, admissibility, insensitivity, ignominiously, amicability, analyticity, antifertility, apparel industry, approachability, business activity, commutability, compressibility, computer industry, construction industry, contemptibility, correlativity, deductibility, despicability, digestibility, duplicability, equatability, excitability, higgledy-piggledy, human activity, illegibility, immutability, impeachability, implausibility, improbability, incapability, inelasticity, infeasibility, inscrutability, insensibility, intangibility, intransitivity, latent hostility, learning ability, mental ability, munitions industry, perceptibility, permutability, practicability, refining industry, reputability, reversibility, shipbuilding industry, social activity, suggestibility, tobacco industry, unfeasibility, unsuitability

7 syllables:
superconductivity, juvenile delinquency, inaccessibility, sexual activity, bioelectricity, bilateral symmetry, anthropocentricity, comprehensibility, hydroelectricity, irresponsibility, radioactivity, lactobacillaceae, static electricity, automobile industry, photoconductivity, special relativity, thermoelectricity, aluminum industry, capital of italy, commercial activity, current electricity, disreputability, doctor of divinity, electronics industry, entertainment industry, imperceptibility, imperishability, imperturbability, impracticability, inadmissibility, inapplicability, incommutability, incompressibility, inconvertibility, indigestibility, indisputability, ineligibility, intelligibility, in all probability, irrepressibility, irreversibility, magical ability, master of divinity, natural ability, offensive activity, physical ability, radial asymmetry, reprehensibility, securities industry, sensory activity, substitutability, subversive activity, unacceptability, unadaptability, unapproachability, unpalatability, unsusceptibility

8 syllables:
theory of relativity, general relativity, piezoelectricity, australian aborigine, bachelor of divinity, civic responsibility, dynamic electricity, indistinguishability, intelligence activity, irrational hostility, performance capability, sense of responsibility, unintelligibility

9 syllables:
atmospheric electricity, educational activity, military capability, operating capability

10 syllables:
coefficient of elasticity, conservation of electricity, extracurricular activity, special theory of relativity, without showing responsibility

11 syllables:
general theory of relativity