impression vs mental picture

impression and mental picture both are nouns.

Word	Noun	Adjective	Verb	Adverb
impression	Yes	No	No	No
mental picture	Yes	No	No	No

As nouns, impression and mental picture are synonyms defined as:

Other synonyms of impression include picture.

impression (noun)	mental picture (noun)
an impressionistic portrayal of a person	a clear and telling mental image
the act of pressing one thing on or into the surface of another
(dentistry) an imprint of the teeth and gums in wax or plaster
an outward appearance
a vague idea in which some confidence is placed
a clear and telling mental image
a symbol that is the result of printing or engraving
all the copies of a work printed at one time
a concavity in a surface produced by pressing