imaginary vs notional

imaginary is a noun but notional is not a noun.

Word	Noun	Adjective	Verb	Adverb
imaginary	Yes	Yes	No	No
notional	No	Yes	No	No

As adjectives, imaginary and notional are synonyms defined as:

imaginary and notional: not based on fact; existing only in the imagination

Other synonyms of imaginary include fanciful.

imaginary (noun)	notional (noun)
(mathematics) a number of the form a+bi where a and b are real numbers and i is the square root of -1

imaginary (adjective)	notional (adjective)
not based on fact; existing only in the imagination	being of the nature of a notion or concept
	indulging in or influenced by fancy
	not based on fact or investigation
	not based on fact; existing only in the imagination