noun
four-corner method
A system for classifying kanji by the shapes of their four corners, used in some dictionaries and input methods. The term is a proper noun referring to this specific indexing method.
四角号碼は、漢字を四隅の形で分類する方法です。
The four-corner method is a way of classifying kanji by the shapes of their four corners.
From Chinese 四角號碼／四角号码 (sìjiǎo hàomǎ), literally 'four-corner code'. The term was adopted into Japanese as a technical name for this indexing system.