TF-IDF是一种统计方法，用以评估一字词对于一个文件集或一个语料库中的其中一份文件的重要程度。字词的重要性随着它在文件中出现的次数成正比增加，但同时会随着它在语料库中出现的频率成反比下降。TF-IDF加权的各种形式常被搜索引擎应用，作为文件与用户查询之间相关程度的度量或评级-

TF-IDF is a statistical method to assess the importance of a word for a file set or a corpus of the importance of one of the documents. The importance of a word increases in proportion to the number of times it appears in a file, but it decreases inversely as it appears in the corpus. The various forms of TF-IDF weighting are often used by search engines as a measure or rating of the degree of correlation between a file and a user query