The kanji 告 primarily conveys the meaning of "to tell," "to inform," "to announce," or "to report." It implies communicating something to someone, often in a formal or official manner. It also carries the sense of declaring or revealing something.

・On-yomi (音読み): コク (koku) ・Kun-yomi (訓読み): つ（げる） (tsu(geru)) – to tell, to inform

⚫︎ 報告（ほうこく） Translation: Report ⚫︎ 広告（こうこく） Translation: Advertisement ⚫︎ 告白（こくはく） Translation: Confession (e.g., of love)

The kanji 告 is a phono-semantic compound (形声文字, けいせいもじ). The semantic component (meaning part) is 口 (kuchi), meaning "mouth," indicating speech or communication. The phonetic component (sound part) is the top part of the character, which originally represented a person kneeling. Thus, the character combines the idea of speech or declaration with the posture of offering or reporting to someone, implying the act of communicating or informing.