In other words, students submit papers to HowNet in the form of word for duplicate checking, and the words hidden by students can be recognized by HowNet, which was jointly developed by Tsinghua University and Tsinghua. Although the system can't recognize the pictures in the text at present, it recognizes the words in word in a special way, not based on the color of the words. This means that HowNet will record the hidden words as the number of words in the full text when calculating the repetition rate of the full text. If there is no repetition of hidden words, the repetition rate of the full text will be reduced to some extent, because hidden words increase the cardinality of the text.