Examples:
cartography
card
archaeology
archetype
monarchy
legal
loyal
purse
personal
cinema
kinase
car
carpenter
hippopotamus
Mesopotamia
dative
data
date
...
Proto-Slavic
*sъ(n)-
→
Old Church Slavonic
съ-
(inherited)
→
Russian
со-
(inherited)
→
Russian
со-
(derived)
→
Russian
снять
(mention)
→
Russian
су-
(cognate)