book · volume

1. Origins, structure, and basic meaning

• Structure: 冊 concerns books or their number of volumes and has the on-reading さつ.
• Basic usage: 冊子(さっし) means a booklet, while 別冊(べっさつ) is a separately bound volume or supplement.

2. Common pitfalls and similar expressions

• Whole-word readings and counting volumes
  • 冊子 is read さっし, with the つ of 冊 changing to a small っ. 別冊 is read べっさつ: the つ in the preceding 別 becomes a small っ, while 冊 retains さつ.
  • One book is counted as 一冊(いっさつ) and two as 二冊(にさつ). Here 冊 is a counter for volumes rather than the noun book.