忘 is composed of two semantic components: 亡 (wáng, "to lose / to perish"), which also suggests the pronunciation, placed under 心 (xīn, "heart/mind"). Together they paint a vivid picture: something has "perished from the mind." This heart-radical construction is shared with many emotion-related characters in Chinese.

In everyday Mandarin, 忘 almost always appears with 了 as 忘了 (wàng le) to mark the completed act of forgetting, or in the compound 忘记 (wàngjì), which is slightly more formal and emphatic. A common filler apology is 我忘了！ ("I forgot!") — instant, colloquial, and universally understood. Be careful not to confuse 忘 (wàng, forget) with the near-homophone 望 (wàng, hope/gaze) — same tone, very different meaning.