Composed of 告 (gào, "to report, to announce") + 诉 (sù, "to speak, to inform"). 告 itself derives from oracle-bone script depicting a mouth facing upward — conveying speech directed at someone. 诉 features the speech radical 讠(言), reinforcing the verbal act of informing.

In Chinese communication culture, the phrasing of "telling" someone something is often softened with hedges or polite forms (e.g., 跟你说 gēn nǐ shuō, "to say to you"). Using 告诉 directly is natural and neutral, but in very formal contexts, 通知 (tōngzhī, "to notify") may be preferred. Note that 告诉 requires a human indirect object — you tell *someone*; you cannot use it for inanimate recipients.