Examples:
cartography
card
archaeology
archetype
monarchy
legal
loyal
purse
personal
cinema
kinase
car
carpenter
hippopotamus
Mesopotamia
dative
data
date
...
Occitan
lum
←
Proto-Indo-European
*léwksmn̥
(inherited)
←
Proto-Indo-European
*lewk-
(mention)
←
Latin
lūmen
(inherited)
←
Old Occitan
(inherited)
→
Catalan
llum
(cognate)
→
Portuguese
lume
(cognate)