Examples:
cartography
card
archaeology
archetype
monarchy
legal
loyal
purse
personal
cinema
kinase
car
carpenter
hippopotamus
Mesopotamia
dative
data
date
...
Greek
οκτώ
←
Ancient Greek
ὀκτώ
(inherited)
←
Proto-Hellenic
*oktṓ
(inherited)
←
Proto-Indo-European
*oḱtṓw
(inherited)
→
German
acht
(cognate)