vegetable patch vs kitchen garden

vegetable patch and kitchen garden both are nouns.

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

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

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

Other synonyms of vegetable patch include vegetable garden.

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