The kanji 洪 primarily conveys the idea of "flood," "vast," "immense," or "great." It represents a large body of water, implying overflowing abundance or overwhelming power, often associated with natural disasters like floods. It can also signify something widespread or plentiful.

・On-yomi (音読み): こう (kō) ・Kun-yomi (訓読み): None, or rarely used as a standalone kun-yomi. The concept is usually expressed through the on-yomi reading.

⚫︎ 洪水 (kōzui) Translation: Flood ⚫︎ 洪大 (kōdai) Translation: Vast; immense; enormous; grand ⚫︎ 洪福 (kōfuku) Translation: Great happiness; immense fortune.

The kanji 洪 is a phono-semantic compound (形声文字, keisei moji). It combines the semantic element of 水 (水, mizu), meaning "water," with the phonetic element 共 (共, kyō), which provides the sound and hints at a related meaning, possibly related to togetherness or sharing, which can be interpreted as something widespread like flood. The water radical suggests the character's association with water and flooding, while the phonetic element gives the pronunciation and a sense of scale. The combination thus points to the character's meaning of great water, or flood.