2 Syllables: SU
7, brethren, cession, crescent, deference, Devon, Essen, essence, Evan, freshened, freshman, heaven, Hessian, leaven, legend, lessen, lesson, peasant, pheasant, pleasant, preference, presence, present, pression, Preston, question, reference, resin, Reverend, session, seven, Stephens, Wesleyan, Weston
3 Syllables: SUU
3 Syllables: USU
accession, aggression, assessment, compression, concession, confession, congestion, contestants, depression, digestion, digression, discretion, equestrian, expression, fluorescent, impression, incessant, ingestion, intestine, investment, obsession, oppression, pedestrian, possession, predestined, procession, profession, progression, quiescence, quiescent, quintessence, recession, refreshment, regression, repression, secession, succession, suggestion, suppression, transgression, unpleasant
4 Syllables: UUSU
acquiescence, adolescence, adolescent, convalescence, convalescent, effervescence, evanescent, incandescent, indigestion, indiscretion, intercession, iridescent, obsolescence, omnipresence, omnipresent, phosphorescent, prepossessions, retrogression
Found 95 words across 4 groupings. Skipped 38 excess words of a similar stem.