kitchen garden vs vegetable garden

kitchen garden and vegetable garden both are nouns.

Word	Noun	Adjective	Verb	Adverb
kitchen garden	Yes	No	No	No
vegetable garden	Yes	No	No	No

As nouns, kitchen garden and vegetable garden are synonyms defined as:

kitchen garden and vegetable garden: a small garden where vegetables are grown

Other synonyms of kitchen garden include vegetable patch.

kitchen garden (noun)	vegetable garden (noun)
a small garden where vegetables are grown	a small garden where vegetables are grown