Hitoe is written as '単衣' or '単' (pronunciation is the same).
It is kimono without lining. According to the custom, it is to be worn only during the months from June to September, however, hitoe made of wool, cotton, or plainly-woven tsumugi-silk are allowed to be worn at other seasons. Hitoe's antonym is 'awase', and especially hitoe made of hemp thread is called 'katabira'. In the Heian period, men wore katabira for soaking up sweat; in the Muromachi period and the Edo period, men and women wore katabira in the shape of kosode (kimono with narrow sleeves).
Hitoe is one kimono without lining of many kimonos forming juni-hitoe (twelve-layered ceremonial kimono).
As forming juni-hitoe, it is worn on kosode(a kimono with short sleeves worn as underclothing by the upper classes) and hakama (pleated loose-fitting trousers)