In literature in the medieval period, sokutai and ikan were not precisely distinguished, but the word 'ikan' may be used to simply mean formal attire of nobles as in the 'ikan tadashiki' (properly wearing ikan).
中世の文献では「衣冠正しき」姿というように、束帯・衣冠を厳密に分けずに、単に貴人の正装の意味でこの言葉を使うこともある。