究

It is a phono-semantic compound, composed of:

穴 (cave, dwelling, hole) – semantic element, suggesting something hidden or enclosed;

九 (gu, “nine”) – phonetic element, also carrying the nuance of something deep or ultimate.

究 depicts the image of probing into a cave (穴) to reach the deepest point (九), symbolizing investigation, study, and pursuit of ultimate truth.

Semantic range:

- to investigate, research – as in 硏究 (연구, research).

- to examine thoroughly, probe deeply – as in 窮究 (궁구, to study and reason out in depth).

- to get to the bottom of, to pursue exhaustively – exploring something to its ultimate end.

It developed into a core character across East Asia meaning “to research, to examine thoroughly, to investigate to the end.”

연구 (硏究) – research, study

궁구 (窮究) – deep investigation, thorough inquiry

탐구 (探究) – exploration, inquiry

연구소 (硏究所) – research institute

䆒 – simplified form using 丸 instead of 九.

𠃙 – variant doubling 九 above and below.