unlined sash
A sash (obi) made of a single layer of fabric, without lining. Typically used in summer or with casual kimono.
An unlined sash is often paired with a summer yukata.
Mixed kanji-kana spelling; less common but still encountered.
Compound of 単 (ひとえ, 'single layer, unlined') and 帯 (おび, 'sash').