noun as adjective

I was told if there is a noun in front of another noun, this means the precedented noun is used as an adjective.

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If I wish to write this sentence in the following forms, what differences will arise?

I was told if there is a noun in front of another noun, this means "the noun that is precedented" is used as an adjective.

OR

I was told if there is a noun in front of another noun, this means "the noun precedented" is used as an adjective.