naive

Concise Oxford English Dictionary © 2008 Oxford University Press:
naive /nʌɪˈiːv, nɑːˈiːv/ (also naïve)

▶adjective

• 1 lacking experience, wisdom, or judgement.

• 2 natural and unaffected.

  ■ (of art) produced in a style which deliberately rejects sophisticated artistic techniques and has a bold directness resembling a child's work.

– derivatives
naively adverb,
naiveness noun,
naivety noun (pl. naiveties).

– origin C17: from Fr. naïve, fem. of naïf, from L. nativus ‘native, natural’.