noun as adjective

0Hi,02br
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00Can a person use a noun with an availble standard adjectival form, which he might not realize the existence of it, can use the noun as an adjective and be considered OK?02br
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00person tutors vs. personal tutors02br
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00institution problems vs. institutional problems02br
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00education materials vs. educational materials02br
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00reflection tasks vs. reflective tasks02br
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00When is the use of available adjectives necessary or a must? What if a person doesn't know the existence of an available adjective? I do admit that those sets of examples seem to give somewhat different impressions in respect to their counter parts but I think, to a person without a keen knowledge of their semantic meanings, the overall impression of phrases might not be all that apparent.0-