Examples:
cartography
card
archaeology
archetype
monarchy
legal
loyal
purse
personal
cinema
kinase
car
carpenter
hippopotamus
Mesopotamia
dative
data
date
...
Middle English
o
→
English
oh
(inherited)
→
English
oh
(inherited)
→
English
-o
(inherited)
→
English
a
(mention)
→
English
O
(mention)