Examples:
cartography
card
archaeology
archetype
monarchy
legal
loyal
purse
personal
cinema
kinase
car
carpenter
hippopotamus
Mesopotamia
dative
data
date
...
Occitan
sièis
←
Proto-Indo-European
*swéḱs
(inherited)
←
Latin
sex
(inherited)
←
Old Occitan
seis
(inherited)