1.Definition: being of the nature of a notion or concept

"To improve notional comprehension", "A notional response to the question"

Related Adjective(s):conceptional, ideational

2.Definition: indulging in or influenced by fancy

"All the notional vagaries of childhood"

Related Adjective(s):fanciful

3.Definition: not based on fact or investigation

"A notional figure of cost helps in determining production costs"

Related Adjective(s):speculative

4.Definition: not based on fact; existing only in the imagination

"To create a notional world for oneself"

Related Adjective(s):fanciful, imaginary