odor vs sense impression

odor and sense impression both are nouns.

Word	Noun	Adjective	Verb	Adverb
odor	Yes	No	No	No
sense impression	Yes	No	No	No

As nouns, sense impression is a hypernym of odor; that is, sense impression is a word with a broader meaning than odor:

odor: the sensation that results when olfactory receptors in the nose are stimulated by particular chemicals in gaseous form
sense impression: an unelaborated elementary awareness of stimulation

Other hypernyms of odor include aesthesis, esthesis, sensation, sense datum, sense experience.

odor (noun)	sense impression (noun)
any property detected by the olfactory system	an unelaborated elementary awareness of stimulation
the sensation that results when olfactory receptors in the nose are stimulated by particular chemicals in gaseous form