The reason we have two words nowadays instead of one is because one of the words is a word that the system just got out of a book, it didn't know what it was and it's going to present it to you.
그런데 요즘엔 한단어 대신 두단어를 보여주는데 그중 하나는 컴퓨터가 디지털화하다가 판독하지 못했던 단어를 보여주는 것이지요.