12. A computer-implemented method, comprising: selecting a topic dictionary comprising topic words related to a topic; determining a topic word divergence value based on a topic word, a document corpus and a topic document corpus, wherein the topic document corpus is a corpus of topic documents related to the topic, and the document corpus is a corpus of documents that includes the topic documents and other documents, and the topic word is a word that is related to the topic; determining a candidate topic word divergence value for a candidate topic word based on the document corpus and the topic document corpus, wherein the candidate topic word is not a topic word in the topic dictionary; and determining whether the candidate topic word is a new topic word for the topic based on the candidate topic word divergence value and the topic word divergence value.
12. A computer-implemented method, comprising: selecting a topic dictionary comprising topic words related to a topic; determining a topic word divergence value based on a topic word, a document corpus and a topic document corpus, wherein the topic document corpus is a corpus of topic documents related to the topic, and the document corpus is a corpus of documents that includes the topic documents and other documents, and the topic word is a word that is related to the topic; determining a candidate topic word divergence value for a candidate topic word based on the document corpus and the topic document corpus, wherein the candidate topic word is not a topic word in the topic dictionary; and determining whether the candidate topic word is a new topic word for the topic based on the candidate topic word divergence value and the topic word divergence value. 14. The method of claim 12 , wherein determining a topic word divergence value comprises: selecting existing topic words in the topic dictionary; determining an existing topic word divergence values for each of the topic words based on the document corpus and the topic document corpus; and determining the topic word divergence value based on a central tendency of the existing topic word divergence values.