1. A method for retrieving based on a search term together with its corresponding meaning from a set of base documents those documents which contain said search term and in which said certain search term has said certain meaning to enable the building of an index on said retrieved documents, said method comprising: searching for those base documents among said set of base documents which contain said certain search term; evaluating the found base documents as to whether said search term contained in said found base documents, respectively, has a certain meaning, said evaluation comprising: generating a text document to represent elements surrounding the search term and their corresponding absolute or relative position with respect to said search term, the elements of said text document coding said absolute or relative positions of said surrounding elements by corresponding text strings; inputting said text document into a trainable classifying apparatus which has been trained to recognize whether an inputted text document belongs to a certain classification category or not, whereas said training has been performed based on a training sample of text documents which have been generated for documents in which the term surrounded by the surrounding elements has said meaning inputted by said user; and classifying said inputted text document to judge whether said search term has said inputted meaning.