Abstract
This paper describes a system and methods to extract synonyms by analyzing Japanese text. One of the extraction methods is based on word co-occurrence similarity of synonyms. Another method detects explanatory expression patterns of synonyms. This system, which uses these two methods, has the advantage that it can apply to large- scale text corpora, because of its robustness. This paper also reports synonym dictionary construction process using this system. The former method tends to extract synonyms of general terms, and the latter method tends to extract abbreviations of proper nouns.