2 syllables:
allness, dullness, dulness, fulness, fulnis, vulnus

4 syllables:
affableness, blamableness, breathableness, culpableness, damnableness, domableness, drinkableness, errableness, friableness, instableness, laudableness, laughableness, likableness, mutualness, notableness, palpableness, peaceableness, placableness, potableness, preferableness, quotableness, ratableness, reasonableness, salvableness, sanableness, savableness, sizeableness, suitableness, tenableness, triableness, tunableness, unableness, versableness, voidableness

5 syllables:
adaptableness, admirableness, adorableness, amenableness, amiableness, amicableness, appeasableness, assailableness, attainableness, availableness, censurableness, comfortableness, commutableness, congealableness, conscionableness, contestableness, controllableness, demonstrableness, deplorableness, detestableness, enjoyableness, estimableness, exceptionableness, excitableness, execrableness, fashionableness, favourableness, formidableness, genericalness, governableness, honourableness, hospitableness, immutableness, implacableness, impregnableness, inclinableness, inculpableness, insanableness, inscrutableness, marketableness, memorableness, mensurableness, palatableness, pardonableness, personableness, pitiableness, questionableness, remarkableness, revocableness, rewardableness, seasonableness, terminableness, treasonableness, unbreakableness, unfashionableness, unspeakableness, unsuitableness, untenableness, veritableness, violableness

6 syllables:
abominableness, associableness, companionableness, determinableness, disciplinableness, dishonourableness, imaginableness, impenetrableness, impressionableness, inalienableness, incalculableness, inconsolableness, indefinableness, indemonstrableness, indissolvableness, indubitableness, inexorableness, inexpiableness, inexpugnableness, inextricableness, interminableness, inviolableness, irreclaimableness, irrefragableness, irrevocableness, objectionableness, reconcilableness, unassailableness, unattainableness, unavoidableness, uncomfortableness, unconscionableness, undeniableness, unexceptionableness, unfathomableness, unfavourableness, unmentionableness, unmistakableness, unnoticeableness, unpalatableness, unprofitableness, unquestionableness, unseasonableness

7 syllables:
disproportionableness, incommensurableness, indecipherableness, indecomposableness, indefatigableness, indeterminableness, irreconcilableness

9 syllables:
area of cardiac dullness

4 syllables:
feasibleness, genus acorus, genus bungarus, genus cebus, genus cedrus, genus chaenomeles, genus chondrus, genus elaeagnus, genus fulmarus, genus juncus, genus mullus, genus pholis, genus ruscus, genus scincus, genus sparaxis, genus squalus, genus thunnus, sweet calamus

5 syllables:
conceivableness

6 syllables:
inconceivableness