注

Phono-semantic compound:

氵(水, 물 수) — semantic, “water, liquid.”

主 (주인 주) — phonetic, also suggesting “to direct, to focus.”

Original sense: to pour or direct a liquid. Extended to “concentrate, pay attention,” and further borrowed in literary usage for “notes, annotations.”

주입 (注入) — to pour in, to inject

주의 (注意) — attention, caution

주목 (注目) — attention, focus

주해 (注解) — annotation, explanatory note

주수 (注水) — water supply, irrigation

Closely related to 註 (“annotation”): in practice, 注 is far more common. 註 is reserved mostly for textual commentary (註釋, 脚註), while 注 is used broadly in everyday words (注目, 注意).

In Japanese and Chinese, 注 is the standard character; 註 is considered non-standard or restricted to specialized contexts.