3 syllables:
flectional, flexional, sectional

4 syllables:
adjectional, affectional, collectional, complexional, connectional, connexional, convectional, correctional, evectional, inflectional, inflexional, inspectional, objectional, perfectional, projectional, protectional, reflectional

5 syllables:
bi-directional, bidirectional, insurrectional, interjectional, intersectional, introspectional, nondirectional, noninflectional, resurrectional, vivisectional

6 syllables:
multidirectional, omnidirectional, uni-directional, unidirectional

3 syllables:
ventricle, helical, despiteful, tenable, equable, estival, medical, stretchable, sensual, skeletal, sextuple, pessimal, sensible, edible, denticle, meltable, vegetable, vendible, retinal, festival, aestival, flexible, spectacle, sentinel, segmental, pedestal, sepulchral, reticle, bendable, sceptical, vesicle, ethnical, legible, credible, pellicle, testicle, methanal, technical, metrical, peccable, epochal, plentiful, seconal, decimal, vegetal, seneschal, genital, skeptical, besprinkle, ethical, pedicel, gettable, centrical, tentacle, testable, jezebel, seminal, rentable, pennoncel, requital, epical, spendable, metical, chemical, pentacle, edental, emmental, getable, kettleful, sellable, vendable, emmenthal

4 syllables:
electrical, impregnable, heretical, acceptable, ineffable, conventicle, dimensional, condemnable, detectable, expressible, alchemical, compensable, congressional, electable, putrescible, dispensable, unethical, preventable, unquenchable, prophetical, genetical, processional, identical, injectable, nonsensical, digestible, adjectival, atenolol, professional, illegible, heliacal, confessional, comestible, inflexible, delectable, insensible, ascendable, defensible, trigeminal, regrettable, contemptible, extendible, defendable, extendable, untenable, ereshkigal, amendable, centesimal, accessible, commendable, amenable, intestinal, respectable, appendicle, collectible, lamentable, expendable, calendrical, correctable, perceptible, receptacle, aesthetical, symmetrical, contestable, obstetrical, execrable, recessional, polemical, ascetical, indelible, incredible, esthetical, angelical, conceptional, dependable, detestable, congenital, ostensible, preferable, impeccable, forgettable, collectable, compressible, susceptible, obsessional, conventional, synthetical, intentional, inedible, exceptional, extensible, church festival, discretional, jazz festival, raw vegetable, redemptional, resplendent quetzel, root vegetable, stand sentinel, unbendable, unrentable, untellable, ascendible, concentrical, ereshkigel, hygienical, nontechnical, poetical, unmedical, untechnical, unvendible

5 syllables:
parenthetical, hexadecimal, unexceptional, geometrical, homiletical, incompressible, petrochemical, apprehensible, imperceptible, comprehensible, exegetical, inextensible, ecumenical, inaccessible, evangelical, undependable, three-dimensional, diametrical, dialectical, neurochemical, indispensable, unconventional, nonprofessional, two-dimensional, unintentional, indigestible, hypothetical, unsymmetrical, inexpressible, reprehensible, irrepressible, alphabetical, catechetical, pyrotechnical, theoretical, indefensible, planetesimal, unforgettable, insusceptible, oecumenical, health professional, asymmetrical, arithmetical, unacceptable, homosexual, unprofessional, antithetical, commonsensible, incontestable, incontestible, leafy vegetable, one-dimensional, third-dimensional, unaccessible, unamenable, uncorrectable, undefendable, undetectable, unexpendable, unexpressible, uninjectable, unpresentable, unpreventable, unrespectable, unsusceptible, algometrical, archangelical, bathymetrical, commonsensical, comprehendible, dietetical, geodesical, isometrical, mnemotechnical, uncollectible, volumetrical

6 syllables:
incomprehensible, semiprofessional, heterosexual, recurring decimal, infinitesimal, repeating decimal, antipathetical, multidimensional, unidimensional, paraprofessional, religious festival, anemometrical, anthropometrical, colorimetrical, photoelectrical, thermoelectrical, uncomprehensible

7 syllables:
circulating decimal, electric receptacle

9 syllables:
bilaterally symmetrical