Kanji for Sun — 日

日 is read hi on its own and nichi or jitsu in compounds. It means the sun, and equally a day — the same character does both jobs, which is why counting days and naming the star share one shape.

Originally a circle with a dot in the middle, brush writing squared it off into today's four strokes. Beside 月 (moon) it makes 明 (bright); above 木 (tree) it becomes 東 (east), the sun rising behind a tree.

日本 (Nihon or Nippon) is Japan — “origin of the sun”, the land the sun comes from as seen from the Chinese mainland, and the reason for the flag. 日曜日 (nichiyōbi) is Sunday, 毎日 (mainichi) every day, 今日 (kyō) today.