• 井戸いど — water well
• 井桁いげた — well frame (井-shaped support structure)
• 天井てんじょう — ceiling
• 市井しせい — the public, townspeople
• 油井ゆせい — oil well

This character originally represented a well — a vital source of water in ancient life. Its cross-grid shape came to symbolize the 9-square land division system in ancient China, representing shared space or organization. It also forms the base of words for social clusters or groupings.

昔むかしは 井戸いどの水みずを使つかって 生活せいかつしていました。
In the past, people used well water for daily life.

市井しせいの人々ひとびとの声こえを大切たいせつにする。
We value the voices of ordinary townspeople.

🎧 The on-yomi セイ and ショウ appear in compounds like 市井 and 天井. The kun-yomi い or いけ is often used in words like 井戸 (well) and 井桁 (well frame).