The kanji 毒 primarily means "poison" or "toxin." It refers to a substance that can cause harm or illness when introduced into a living organism. It also conveys the concept of something harmful, dangerous, or detrimental in a figurative sense.

・On-yomi (音読み): ドク (doku) ・Kun-yomi (訓読み): None, or the meaning is expressed directly as 毒 (doku).

⚫︎ 毒薬 (dokuyaku) Translation: poison; toxic medicine ⚫︎ 有毒 (yūdoku) Translation: poisonous; toxic ⚫︎ 毒舌 (dokuzetsu) Translation: sharp tongue; venomous speech

I am unable to provide information about the correspondence with Vietnamese.

The kanji 毒 is a phono-semantic compound (形声文字, keisei moji). The radical (部首, bushu) is 歹 (gatsu, gai), which signifies "death" or "decay." The phonetic component is 幸 (kou, sai). This suggests the initial meaning of 毒, which is something that brings about death or is dangerous to health. The combination of the radical 歹, which provides the semantic element of "harm" or "illness," and the phonetic element 幸, which contributed to the sound and subtly hinted at the concept, created the character for "poison."