“Extra issue” in Japanese
Short answer
Extra issue in Japanese is “臨時増刊” (rinjizoukan). Full meaning: extra (special) issue (e.g. of a magazine).
Other ways to say “Extra issue” in Japanese
別冊
bessatsu separate volume, extra issue, supplement, additional volume, supplementary volume
別巻
bekkan separate volume, extra issue
増刊号
zoukangou special issue, extra issue, special number
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