2 Syllables: SU
7, 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.