Or search: aeriform, aery, airy, antenna, botany, ethereal, flare, insubstantial, phytology, receiver, sender, transmitter, unreal, unsubstantial
2 Syllables: SU
ariel, 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
secretarial

Found 24 words across 3 groupings. Skipped 4 excess words of a similar stem.