adjective
BAD : People tend to become less imaginary as they grow older.
GOOD : People tend to become less imaginative as they grow older.
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imaginary = not existing in real life but only in someone's mind: 'This new novel takes the reader on an imaginary journey into space.' 'The little boy kept firing an imaginary gun at me.'
imaginative = having or showing a powerful imagination: 'She is one of the most imaginative designers of her generation.' 'His paintings tend to be highly imaginative.'