syn- /sin-/, sy- /si-/, syl- /sil-/, sym- /sim-/ or sys- /sis-/

Signifying together, with

• belt bags
• belt drive
• belt drives
• belted
• belter
• belters
• belting
• beltings
• beltman
• beltmen
• belt out
• belts
• belt-tightening
• belt up
• beltway
• beltways
• beluga
• belugas
• belvedere
• belvederes
• belying
• bel étage
• BEM
• brokery
• brokes