[mass noun]a paper size, 564 × 444 mm (纸张尺寸标准)564 × 444 mm ■(全称 demy octavo)a book size, 216 × 138 mm (书开本)八开本216 × 138 mm ■(全称 demy quarto)a book size, 276 × 219 mm (书开本)四开本(276× 219 mm)
语源
late Middle English (as an adjective in the sense 'half-sized'): from demi-, or from its source, French demi 'half'