3 syllables:
-cephalous, cephalous, cephalus

4 syllables:
acephalous, acephalus, bicephalous, bicephalus, bucephalus, dicephalous, dicephalus, encephalous, poicephalus, tricephalous, tricephalus

5 syllables:
acrocephalous, acrocephalus, androcephalous, anencephalous, anencephalus, arctocephalus, aurocephalous, autocephalous, brachycephalous, chirocephalus, conocephalus, cynocephalous, cynocephalus, diplocephalus, epinephelus, ganocephalous, hetercephalous, hydrocephalous, hydrocephalus, leptocephalous, leptocephalus, macrencephalous, macrocephalous, macrocephalus, megacephalous, mesocephalous, micrencephalous, microcephalous, microcephalus, monocephalous, monocephalus, myxocephalus, nanocephalous, perocephalus, platycephalous, pneumocephalus, podocephalous, pyrocephalus, sarcocephalus, scaphocephalous

6 syllables:
acanthocephalous, argyrocephalous, bothriocephalus, ctenocephalus, euoplocephalus, gorgonocephalus, heterocephalus, hydroencephalus, megalocephalous, mesaticephalous

7 syllables:
dibothriocephalus

3 syllables:
emphasis, nebulous, elements, hephaestus, tetanus, sedulous, petulance, offenseless, fecklessness, membranous, restlessness, excellence, exodus, evidence, pendulous, recklessness, edifice, detritus, blessedness, helplessness, renascence, precedence, helpfulness, pestilence, tremulous, prevalence, eminence, tenebrous, fretfulness, aesculus, pegasus, endlessness, resinous, credulous, resonance, dreadfulness, elephants, eloquence, pleasantness, regulus, daedalus, gentleness, healthfulness, precipice, petalous, specialness, negligence, tendinous, tenuous, emulous, femaleness, genesis, xenopus, venomous, benelux, elegance, relevance

4 syllables:
contentiousness, benevolence, inelegance, antecedence, preeminence, beneficence, unpleasantness, affectedness, apetalous, directionless, edematous, shigellosis, state's evidence, maleficence, pink elephants, persepolis, incredulous, irrelevance, intelligence, malevolence, eleven-plus, necessitous

5 syllables:
atelectasis, conscientiousness, hearsay evidence, direct evidence, overemphasis

6 syllables:
magnetic resonance, indirect evidence, dicotyledonous

7 syllables:
circumstantial evidence

8 syllables:
artificial intelligence