If you use “noun” as adjective, it means that the noun that you are using is acting as an adjective. Unless the noun you are going to use is in fixed plural form for example: “news” report (singular) / “news” reports (plural) or “accounts” clerk (singular) / “accounts” clerks (plural) then it is not advisable to put such nouns you are using for adjectives in plural.

In your examples:-

“bags hands” - do you mean bag’s handles? or do you want to say handbags? “bads hands” in itself does not make proper English sense.

“legumes varities” - you can make your sentence for example “we have a few varieties of legumes for your choice” but if you insist on saying in this context then you should say “legume varieties” instead, meaning “legume” without the “s”. For examples your sentence can be like this “The shop’s legume varieties are very limited.”

I hope this can help you understand “nouns as adjectives” more clearly.

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