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

Signifying together, with

• frustrated
• frustrated export
• frustrates
• frustrating
• frustratingly
• frustration
• frustrations
• frusts
• frustule
• frustules
• frustum
• frustums
• frutex
• frutices
• fruticose
• frutified
• frutifies
• frutify
• frutifying
• fry
• fryer
• fryers
• frying
• frying-pan
• frying-pans