2 Syllables: SU
biggest, bigots, bilious, billets, biscuits, bishops, Christmas, citrus, dearest, digits, fittest, frigates, grimace, hillocks, illness, isthmus, limits, listless, minutes, minutest, mistress, nearest, Nicholas, nitrous, Philips, pickets, quibus, richest, rivets, spinach, stillness, thickets, tickets, vicious, village, villas, viscous
3 Syllables: USU
ambitious, archbishops, assiduous, auspicious, bacillus, capricious, delicious, elicits, exhibits, factitious, fictitious, inhibits, judicious, malicious, Narcissus, nutritious, officious, pernicious, prestigious, prodigious, prohibits, propitious, punctilious, religious, seditious, severest, sincerest, suspicious, utilise
4 Syllables: UUSU
adventitious, avaricious, expeditious, injudicious, irreligious, supercilious, superstitious, surreptitious, unpropitious, unsuspicious
Found 76 words across 3 groupings. Skipped 3 excess words of a similar stem.