Lack of sophistication, experience, judgement or worldliness; artlessness; gullibility; credulity. (noun)
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Use "naïveness" in a sentence
"I expect the naiveness from the college kids, but you adults who have been voting for awhile should know better!"
"Maybe young and stupid sometimes, but sometimes that naiveness, it's a little scary."
"Too little too late, Obama has lost the people he needs to win in November, his lies, constant flip flops, and naiveness … All on video, they will rip him apart once the nomination is over, and it will all be his fault."