2 Syllables: SU
aerial, barrel, burial, careful, Carol, Carroll, Gerald, Harold, Herald, Merrill, peril, prayerful, sterile
3 Syllables: USU
biennial, Centennial, Ezekiel, Fitzgerald, imperil, imperilled, malarial, perennial, terrestrial, triennial
4 Syllables: UUSU
Found 24 words across 3 groupings. Skipped 4 excess words of a similar stem.