The realization that each random passerby is living a life as vivid and complex as your own.

Origin: The word 'sonder' is a neologism coined by John Koenig for his project 'The Dictionary of Obscure Sorrows', which aims to fill in gaps in the English language by creating words for emotions that currently lack a term. Although 'sonder' is not derived from historical linguistic evolution, it is crafted to sound like it belongs in English, combining familiar phonetic elements.
Historical and Cultural Context: First appearing in Koenig's project around 2012, 'sonder' quickly resonated with people online, capturing a universal yet often unarticulated human experience. It reflects a growing cultural awareness and empathy facilitated by global connectivity.
Evolution: As a modern creation, 'sonder' doesn't have a history of phonetic or semantic shifts. However, its widespread adoption into everyday language showcases the dynamic and evolving nature of English vocabulary, influenced by contemporary culture and media.
Modern Relevance: Today, 'sonder' is used to express a profound moment of realization in literature, social media, and personal reflections. It has become a part of contemporary lexicon, often appearing in discussions about empathy and human interconnectedness.

The word 'sonder' is not officially recognized in major dictionaries but is widely understood and used, highlighting the power of language to evolve and capture complex emotions.