Examples:
cartography
card
archaeology
archetype
monarchy
legal
loyal
purse
personal
cinema
kinase
car
carpenter
hippopotamus
Mesopotamia
dative
data
date
...
Cornish
kath
←
Proto-Brythonic
*kaθ
(inherited)
←
Proto-Celtic
*kattā
(inherited)
→
English
cat
(cognate)