Or search: stratum
2 Syllables: SU
jointly, loyally, loyalties, loyalty, noisy, oily, royally, royalties, royalty
3 Syllables: USU
adroitly, conjointly, disloyalty, employee
3 Syllables: UUS
appointees

Found 14 words across 3 groupings. Skipped 1 excess word of a similar stem.