synesthesia vs aesthesis

synesthesia and aesthesis both are nouns.

Word	Noun	Adjective	Verb	Adverb
synesthesia	Yes	No	No	No
aesthesis	Yes	No	No	No

As nouns, aesthesis is a hypernym of synesthesia; that is, aesthesis is a word with a broader meaning than synesthesia:

synesthesia: a sensation that normally occurs in one sense modality occurs when another modality is stimulated
aesthesis: an unelaborated elementary awareness of stimulation

Other hypernyms of synesthesia include esthesis, sensation, sense datum, sense experience, sense impression.

synesthesia (noun)	aesthesis (noun)
a sensation that normally occurs in one sense modality occurs when another modality is stimulated	an unelaborated elementary awareness of stimulation