2 Syllables: SU
aaron, baron, barren, beckon, bedlam, bellum, bremen, brethren, breton, cession, clarence, clemens, clement, crescent, currant, deaden, deference, devon, edwin, ellen, errand, errant, essen, essence, evan, felon, freshened, freshman, harem, heaven, helen, heron, hessian, karen, leaden, leaven, leben, legend, lemon, lenin, lessen, lesson, melon, parent, peasant, pelham, penance, pennant, pheasant, pleasant, plenum, preference, presence, present, pression, preston, question, reckon, reddened, reference, resin, reverend, second, session, seven, sharon, stephens, tenant, terence, threaten, vellum, venom, veteran, weapon, weren, wesleyan, weston
3 Syllables: SUU
3 Syllables: USU
aberrant, accession, aggression, apparent, assessment, compression, concession, confession, congestion, contestants, depression, digestion, digression, discretion, equestrian, expression, fluorescent, forbearance, impression, incessant, ingestion, inherent, intestine, investment, lieutenant, magellan, obsession, oppression, pedestrian, possession, predestined, procession, profession, progression, quiescence, quiescent, quintessence, recession, refreshment, regression, repellent, repression, secession, succession, suggestion, suppression, transgression, transparent, unpleasant, unquestioned
4 Syllables: UUSU
acquiescence, adolescence, adolescent, cerebellum, convalescence, convalescent, effervescence, evanescent, incandescent, indigestion, indiscretion, intercession, iridescent, mahometan, obsolescence, omnipresence, omnipresent, phosphorescent, prepossessions, retrogression
Found 150 words across 4 groupings. Skipped 57 excess words of a similar stem.