Examples:
cartography
card
archaeology
archetype
monarchy
legal
loyal
purse
personal
cinema
kinase
car
carpenter
hippopotamus
Mesopotamia
dative
data
date
...
Bulgarian
твърд
←
Proto-Slavic
*tvьrdъ
(inherited)
←
Proto-Slavic
*tvьrdь
(inherited)
→
Russian
твердь
(cognate)