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

Signifying together, with

• hacklets
• hacklier
• hackliest
• hackling
• hack-log
• hack-logs
• hackly
• hackmatack
• hackmatacks
• hackney
• hackney cab
• hackney cabs
• hackney carriage
• hackney carriages
• hackney coach
• hackney coaches
• hackney-coachman
• hackney-coachmen
• hackneyed
• hackneying
• hackneyman
• hackneymen
• hackneys
• hacks
• hacksaw