Mark and Dorothy (3)
I believe the answer is:
dot
I believe this is a double definition.
'mark' is the first definition.
(I know that dot is a type of write)
'dorothy' is the second definition.
(nickname for someone called Dorothy)
'and' is the link.
(Other definitions for dot that I've seen before include "A point, small round mark" , "scatter" , "Very small circular shape" , "Tiny speck" , "One signal used in Morse code" .)