soft diet vs spoon food

soft diet and spoon food both are nouns.

Word	Noun	Adjective	Verb	Adverb
soft diet	Yes	No	No	No
spoon food	Yes	No	No	No

As nouns, soft diet and spoon food are synonyms defined as:

soft diet and spoon food: a diet that does not require chewing; advised for those with intestinal disorders

Other synonyms of soft diet include pap.

soft diet (noun)	spoon food (noun)
a diet that does not require chewing; advised for those with intestinal disorders	a diet that does not require chewing; advised for those with intestinal disorders