noun
issue number; size number
Refers to the number assigned to a periodical issue or the size designation of pictures, paper, or type. Often used in contexts like magazine issue numbers or photo print sizes.
この雑誌の最新号数は何ですか。
What is the latest issue number of this magazine?
写真の号数が大きいほど、プリントのサイズも大きくなります。
The larger the size number of the photo, the larger the print size.