Left tortoise shell bracket

It marks an insertion, annotation, or formal label.

In Japanese editorial practice, 〔…〕 inserts an editor’s or translator’s supplement inside quoted material. Chinese punctuation guidance uses the pair for an author’s dynasty, a government document year, or a note. Read the enclosed words as information added around the main text, not as the speaker’s own words.

Chinese calls it 六角括号, the six-angle bracket; a Beijing Normal University publishing-history overview places its standardized use in the Qing period, China’s last imperial dynasty. Japanese calls it 亀甲括弧 (kikkō kakko, tortoise-shell bracket), and Japanese layout guidance treats 〔〕 as the vertical-writing counterpart of the square bracket ［］.

Why is 〔 sometimes used without 〕?

Because placement can turn the opener into a line marker.

In a 2019 discussion of a Chinese play script, a line-initial 〔 marks non-dialogue text such as stage directions; it is not half of a pair. In Japanese quoted prose, read 〔…〕 as a matched insertion and expect 〕. In formal Chinese prose, a nearby year, dynasty name, or note makes a label more likely than a broken pair.