Duplicate — twin (8)
I believe the answer is:
parallel
I believe this is a double definition.
'duplicate' is the first definition.
(I know that duplicate can be written as parallel)
'twin' is the second definition.
(I know that twin can be written as parallel)
(Other definitions for parallel that I've seen before include "Similarity, comparison" , "Continuously at equal distances apart" , "bars in gym?" , "Maintaining distance apart" , "Of two lines, continuously at same distance apart" .)