WordNet是一个由普林斯顿大学认识科学实验室在心理学教授乔治·A·米勒的指导下创建和维护的英语字典。开发工作从1985年开始，从此以后该项目接受了超过300万美元的资助（主要来源于对机器翻译有兴趣的政府机构）。

由于它包含了语义信息，所以有别于通常意义上的字典。WordNet根据词条的意义将它们分组，每一个具有相同意义的字条组称为一个synset（同义词集合）。WordNet为每一个synset提供了简短，概要的定义，并记录不同synset之间的语义关系。

WordNet的开发有两个目的：

WordNet的数据库及相应的软件工具的发放遵照BSD许可证书，可以自由的下载和使用，亦可在线查询和使用。

WordNet is a lexical database for the English language. It groups English words into sets of synonyms called synsets, provides short definitions and usage examples, and records a number of relations among these synonym sets or their members. WordNet can thus be seen as a combination of dictionary and thesaurus. While it is accessible to human users via a web browser, its primary use is in automatic text analysis and artificial intelligence applications. The database and software tools have been released under a BSD style license and are freely available for download from the WordNet website. Both the lexicographic data (lexicographer files) and the compiler (called grind) for producing the distributed database are available.