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

Signifying together, with

• retroflexes
• retroflexing
• retroflexion
• retroflexions
• retrogradation
• retrogradations
• retrograde
• retrograded
• retrogradely
• retrogrades
• retrograding
• retrogress
• retrogressed
• retrogresses
• retrogressing
• retrogression
• retrogressional
• retrogressions
• retrogressive
• retrogressively
• retroject
• retrojected
• retrojecting
• retrojection
• retrojections