Japan has a word for the anxiety of not replying to messages: 'sonder'

Japan has coined numerous words for emotional states with no English equivalent. 'Tsundoku' means buying books and never reading them. 'Wabi-sabi' is finding beauty in imperfection. 'Mono no aware' is the gentle sadness of things passing. Each reflects cultural priorities invisible in English — evidence that emotion and language are deeply entangled.

Source: The Dictionary of Obscure Sorrows / NHK World — Japanese cultural reporting