Hypothetical or imaginary (8)
I believe the answer is:
notional
I believe this is a double definition.
'hypothetical' is the first definition.
(synonyms)
'imaginary' is the second definition.
(I know that imaginary can be written as notional)
(Other definitions for notional that I've seen before include "Hypothetical, imaginary" , "Unreal" , "Hypothetical, assumed to be correct" , "La Gioconda" , "Existing as theory, not existing in reality" .)