Examples:
cartography
card
archaeology
archetype
monarchy
legal
loyal
purse
personal
cinema
kinase
car
carpenter
hippopotamus
Mesopotamia
dative
data
date
...
Cornish
sevi
←
Proto-Celtic
*subi
(inherited)
←
Old Cornish
syvyen
(inherited)
→
Welsh
syfi
(cognate)
→
Cornish
sevien
(suffix)