出处：按学科分类—语言、文字 中国对外翻译出版公司《汉英成语词典》第290页（226字）
不能分辨豆或麦，比喻愚昧无知，例他不辨菽麦，偏偏好为人师，结果既害别人，也害了自己。
Though he knows nothing about practical matters，he loves to lecture others．No one benefits from his chitter-chatter，not even himself．