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1. Not based on fact; existing only in the imagination
   "to create a notional world for oneself";
   - fanciful, imaginary
    
2. Not based on fact or investigation
   "a notional figure of cost helps in determining production costs";
   - speculative
    
3. Indulging in or influenced by fancy
   "all the notional vagaries of childhood";
   - fanciful
    
4. Being of the nature of a notion or concept
   "to improve notional comprehension"; "a notional response to the question";
   - conceptional, ideational

See also: abstract, creative, originative, theoretic, theoretical, unreal

Encyclopedia: Notional