What 구 means
Translate 구 in the context of the whole Korean word. Hanja (Chinese characters used in Korean) link it to separate roots: 九, “nine”; 區, “district”; and 舊, “old/former.” In 구간 (“old edition”), 구 carries the last root.
The first written record of Hangul’s creation is from 1443. King Sejong made it to help people who found Chinese characters difficult write Korean; the explanatory book Hunminjeongeum appeared in 1446.
When software standardizes text (Unicode normalization), it can decompose 구 into two Korean letters, ᄀ and ᅮ; together, they still form one syllable.
Questions people ask
1Why does 구 show as a box on some devices?
Because that device's fonts have no glyph for it. The character is still correct and still copies correctly — the box is a missing glyph, not a broken character.
How to type 구
구\AD6CCodes and encoding1 code points
A visible symbol can contain several code points. JS .length counts UTF-16 units; UTF-8 counts bytes.

