7 letters:
clivity, privity

8 letters:
activity, motivity, nativity

9 letters:
acclivity, captivity, clusivity, declivity, erosivity, festivity, passivity

10 letters:
adaptivity, coactivity, emissivity, ergativity, inactivity, negativity, proclivity, reactivity, relativity

11 letters:
affectivity, agressivity, bioactivity, corrosivity, deceptivity, diffusivity, directivity, effectivity, exclusivity, expansivity, impassivity, impulsivity, inclusivity, inductivity, infectivity, infestivity, normativity, objectivity, obsessivity, proactivity, receptivity, recessivity, recursivity, reflexivity, reluctivity, resistivity, retentivity, selectivity, sensitivity

12 letters:
absorptivity, aggressivity, attractivity, collectivity, conductivity, connectivity, exhaustivity, expressivity, generativity, intinctivity, overactivity, perceptivity, perfectivity, permittivity, processivity, productivity, projectivity, reflectivity, refractivity, regressivity, responsivity, sex activity, subjectivity, susceptivity, transitivity, vasoactivity

13 letters:
alternativity, associativity, commutativity, cooperativity, correlativity, destructivity, evaporativity, hyperactivity, insensitivity, instinctivity, interactivity, perspectivity, progressivity, radioactivity, retroactivity, self-activity, superactivity, underactivity

14 letters:
human activity, incogitativity, intempestivity, interpassivity, intransitivity, performativity, radio-activity, reproductivity, seronegativity, seropositivity, transmissivity

15 letters:
impredicativity, oversensitivity, sexual activity, social activity

16 letters:
amatonormativity, chemoreceptivity, chemosensitivity, cross-reactivity, immunoreactivity, pyroconductivity, regioselectivity, sensory activity

17 letters:
anticommutativity, business activity, electronegativity, heteronormativity, intersubjectivity, photoconductivity, stereoselectivity, superconductivity

18 letters:
enantioselectivity, general relativity, offensive activity, special relativity

19 letters:
commercial activity, electroconductivity, subversive activity

20 letters:
educational activity, theory of relativity

21 letters:
human sexual activity, intelligence activity

24 letters:
extracurricular activity

28 letters:
general theory of relativity, special theory of relativity

5 letters:
italy

6 letters:
infamy, wicopy, dimity, wiggly, fixity, litany, bigamy, sicily, simile

7 letters:
visibly, timpani, tiffany, utility, timothy, willowy, dittany, acidity, aridity, fidgety, vividly, trilogy, finicky, trinity, imagery, bigotry, ability, avidity, dingily, mistily, rickety, dignity, tripoli, timidly, agility, infancy, syncope, giddily, dizzily, epitome, hymnody, licitly, millime, ribbony, twinkly, windily, wriggly

8 letters:
polygyny, futility, symphony, vicinity, visually, tinselly, salinity, exiguity, sympathy, virility, stickily, solidity, signally, rigidity, ministry, rapidity, tumidity, vapidity, toxicity, fluidity, humidity, timidity, filigree, civility, symmetry, affinity, stingily, sapidity, senility, brittany, infinity, instancy, villainy, dismally, epiphany, docility, industry, fiscally, wilfully, polygamy, tepidity, felicity, antigone, tonicity, validity, finitely, mobility, minutely, viridity, nobility, debility, piquancy, divinity, chivalry, infantry, exigency, acridity, bishopry, filthily, flindosy, frigidly, gelidity, prissily, trickily, viscidly

9 letters:
viscidity, facsimile, hostility, synchrony, torridity, indignity, antiquity, publicity, invisibly, flippancy, viciously, liquidity, atonicity, instantly, turbidity, fragility, antipathy, cyclicity, initially, fertility, polyphony, torpidity, soliloquy, abysmally, miserably, proximity, limpidity, turgidity, inutility, placidity, literally, willfully, aborigine, immorally, liberally, unanimity, viability, prolixity, culicidae, ductility, asymmetry, morbidity, irritably, chintzily, lingually, malignity, rusticity, skilfully, stolidity, tactility, winsomely

10 letters:
skillfully, magistracy, benignancy, gravimetry, malignancy, stringency, implicitly, alkalinity, resiliency, amiability, originally, brilliancy, elasticity, spitefully, deficiency, spasticity, officially, complicity, volatility, asynchrony, legibility, invalidity, infelicity, simplicity, flaccidity, pasigraphy, flippantly, insipidity, femininity, explicitly, sphericity, somniloquy, efficiency, capability, forgivably, imbecility, insistency, mendicancy, minstrelsy, mutability, notability, pipal tree, plasticity, risibility, sanguinity

11 letters:
proficiency, alkalimetry, whiffletree, contingency, reliability, masculinity, obstinately, astringency, pellucidity, probability, periodicity, domesticity, antistrophe, ambitiously, brilliantly, delinquency, deliciously, magnanimity, apocynaceae, ellipticity, versatility, religiously, catholicity, electricity, intrepidity, sufficiency, calorimetry, feasibility, whippletree, differently, flexibility, possibility, amphictyony, specificity, swingletree, consistency, colorimetry, efficiently, calligraphy, amicability, analyticity, permissibly, persistency, persnickety, propinquity, quizzically, quotability, stringently, syllabicity, tangibility, unthinkably, ventriloquy

12 letters:
sufficiently, idiosyncrasy, invisibility, eccentricity, auspiciously, unofficially, individually, perniciously, inefficiency, availability, artificially, sweet cicely, malleability, holy trinity, deliberately, peripherally, additionally, consistently, chromaticity, irritability, fortuitously, adaptability, palatability, irresistibly, propitiously, avariciously, equatability, excitability, illegibility, immutability, incapability, inelasticity, inhospitably, oil industry, reputability, semifluidity, shittah tree, toy industry, unforgivably

13 letters:
intermittency, compatibility, cucurbitaceae, expeditiously, insufficiency, contractility, conditionally, unequivocally, supersymmetry, injudiciously, acceptability, applicability, pusillanimity, inconsistency, promiscuously, traditionally, inefficiently, unchristianly, admissibility, ignominiously, antifertility, arms industry, coal industry, commutability, concentricity, consanguinity, deductibility, despicability, digestibility, duplicability, film industry, impermissibly, improbability, ineligibility, infeasibility, insensibility, intangibility, permutability, reversibility, shoe industry, sign industry, unambitiously, unfeasibility, unpredictably, unsuitability, with sympathy, with validity

14 letters:
inauspiciously, superciliously, insufficiently, susceptibility, bioelectricity, meretriciously, perfectibility, responsibility, public utility, impeachability, implausibility, inconsistently, inscrutability, mental ability, mental imagery, movie industry, perceptibility, practicability, sapodilla tree, steel industry, stretchability, suggestibility, taoist trinity, unadaptability, unpalatability, unpropitiously, with hostility

15 letters:
radial symmetry, surreptitiously, inaccessibility, neuropsychiatry, growth industry, unconditionally, approachability, blessed trinity, compressibility, contemptibility, disreputability, granadilla tree, imperishability, inadmissibility, inapplicability, incommutability, indigestibility, indisputability, intelligibility, irreversibility, magical ability, mass deficiency, mirror symmetry, natural ability, put differently, unacceptability, with efficiency, zinc deficiency

16 letters:
self-sufficiency, piezoelectricity, hydroelectricity, irresponsibility, lactobacillaceae, service industry, apparel industry, banking industry, capital of italy, chondrodystrophy, fashion industry, housing industry, imperceptibility, imperturbability, impracticability, inconvertibility, irrepressibility, latent hostility, learning ability, physical ability, radial asymmetry, reprehensibility, substitutability, tobacco industry, unsusceptibility, without sympathy

17 letters:
relative humidity, comprehensibility, chemical industry, joint probability, mental deficiency, thermoelectricity, aluminum industry, computer industry, higgledy-piggledy, incompressibility, lighting industry, plastics industry, refining industry, trucking industry, unapproachability, unintelligibility

18 letters:
bilateral symmetry, anthropocentricity, muscular dystrophy, static electricity, doctor of divinity, in all probability, master of divinity, munitions industry

19 letters:
automobile industry, current electricity, dynamic electricity, military capability, securities industry

20 letters:
juvenile delinquency, australian aborigine, bachelor of divinity, civic responsibility, electronics industry, indistinguishability, irrational hostility, operating capability

21 letters:
construction industry, shipbuilding industry

22 letters:
entertainment industry, performance capability

23 letters:
atmospheric electricity, sense of responsibility

25 letters:
coefficient of elasticity

27 letters:
conservation of electricity

30 letters:
without showing responsibility