What is define sonder?

Sonder is a made-up word created by John Koenig, an author and video producer who is known for creating a dictionary of made-up words that describe feelings and emotions that don't have a word in the English language. The word sonder means the realization that each passerby has a life as complex as one's own, with their own thoughts, feelings, and experiences. It is the feeling of not being the center of attention, but just one of many people sharing the world and experiencing it in their own unique way. The word has gained popularity in recent years and is often shared on social media as a way to reflect on the interconnectedness of all humanity.