The swallow hieroglyph is also an ideogram for the swallow birds. Originally an ancient ideogram, some people think it is a pictographic syllable. Mathematical symbols are a type of ideogram. During the Sasanian Empire (226-651), the ideogram signified a free (i.e. non-slave) peasant of Mesopotamia. The Japanese language uses "W", pronounced , as an ideogram meaning "double". There was a pattern on the front side which looked like ideogram. "Shuowen Jiezi" dictionary, was a rare "huiyi" "compound ideogram" or "ideogrammic compound". There was a second ideogram to distinguish the models. Also, as an ideogram in the Egyptian word "city", "niwt". The sign is also an ideogram for 'face', and related words. In fact, the building is also called an "urban ideogram". Linear B also includes, inter alia, an ideogram for wine, i.e. . Unger disputes claims made on behalf of Blissymbols in his 2004 book "Ideogram".