Recently, e-learning systems for self-learning with various types of retrieval functions have been developed. This paper describes a method for keyword extraction using retrieval information stored from many students through the retrieval functions. Firstly, we show that (1) teachers tend to consider technical terms as important, while students unfamiliar with the technical terms tend to retrieve the terms, therefore (2) there is a clear correlation between keywords extracted by the teachers and the retrieval words by the students. Secondly, we propse a method utilizing retrieval information from the students for keyword extraction, and show that the mehod can achieve quite better performance than a method extracting keywords using only lecture information.
