dietetic vs diet

dietetic is not a noun while diet is a noun.

Word	Noun	Adjective	Verb	Adverb
dietetic	No	Yes	No	No
diet	Yes	No	Yes	No

dietetic (noun)	diet (noun)
	the act of restricting your food intake (or your intake of particular foods)
	a prescribed selection of foods
	the usual food and drink consumed by an organism (person or animal)
	a legislative assembly in certain countries (e.g., Japan)

dietetic (adjective)	diet (adjective)
of or relating to the diet

dietetic (verb)	diet (verb)
	eat sparingly, for health reasons or to lose weight
	follow a regimen or a diet, as for health reasons