Kanji for Peace — 和

和 is read wa and carries harmony, calm and peace — but the word Japanese actually uses for peace between nations is 平和 (heiwa), where 和 is paired with 平 (flat, level). On its own, 和 is closer to things being in balance with each other than to the absence of war.

The character is a stalk of grain (禾) beside a mouth (口): everyone fed, everyone in agreement. That reading is folk etymology as much as scholarship, but it matches how the word is used — 和む (nagomu) means to relax, to soften, the feeling of tension leaving a room.

和 is also the old name of Japan itself, which is why it prefixes anything traditionally Japanese: 和食 (washoku) is Japanese cuisine, 和室 (washitsu) a tatami room, 和紙 (washi) handmade paper. Emperors' eras use it too — 昭和 (Shōwa) and 令和 (Reiwa) both contain it. So a lone 和 says harmony and Japaneseness at once.