The fourth group represented by "Teikin Orai" comprises books of words and knowledge in the style of letters, which aimed to spread necessary knowledge as well as the form of letters.
『庭訓往来』に代表される書簡形式を採った単語集・知識集で、書簡の形式とともに必要な知識を身に付けさせる事を目指したもの。